Seeing that it was a history book, a male tutor smiled and said, "I don't know when you became interested in history?"
"Haven't you been researching innovative technologies for three-dimensional weapons?"
Xiaojie pointed at the history book on top and said, "Energy, in this world, there is energy that can replace 'Star Crystal'!"
A mentor with a handsome mustache laughed and said, "You're looking for alternative energy sources in history books?"
Xiao Jie flipped open the book and said, "Yes, history has long pointed out to us the existence of new alternative energy sources."
"If we don't have these, then what do we use before we have ectoplasm crystals?"
The female instructor who had wanted Xiaojie to leave frowned and said, "That makes sense. So what did you find?"
Xiaojie looked up: "Coal!"
He said loudly: "Before the appearance of 'ectoplasm crystals', before the 'sublimation era', the world suffered a terrible disaster that almost destroyed the entire world."
The mustache mentor laughed and said, "I know that."
"'Black Disaster'..."
"Suddenly one day, a small town disappeared, and many people lost contact with their relatives in the town."
“So some people headed for the town.”
"Not long after, the man escaped and came back, saying that everyone in the town had disappeared, even the town itself."
"The whole town was left with only a dark patch of ground."
"No one believed what this man said at the time, but soon, similar disasters occurred in other towns and even cities."
A middle-aged mentor took over and said: "The darkness spread across the world. Wherever it passed, everything collapsed. Whether it was humans, animals or plants, they all disappeared in this darkness."
Xiaojie nodded: "Yes, this is the 'Black Disaster'."
"But this disaster suddenly stopped one day, and then more than ten years later, the first Clave Gate appeared."
"From then on, mankind entered the 'Age of Ascension'."
"However, between the end of the 'Black Disaster' and the beginning of the 'Sublimation Era', people had already found a solid fuel that could generate heat and provide energy."
"That's coal. It's a combustible organic rock. It's a combustible mineral that was gradually formed when ancient plants were buried underground and underwent complex changes."
"Long before the emergence of the 'Sublimation Age', before the utilization of ectoplasmic crystals, people knew about the existence of coal and used it effectively."
“Now, should we repurpose this energy?”
Xiaojie said excitedly: "The disappearance of the Clave Gate indicates that a new era has arrived."
“Whoever can master this kind of mineral deposits in large quantities in the early stage and master new energy will be able to gain a firm foothold in the new era!”
Several mentors kept nodding.
The man with the mustache said, "I will go inform the city lord right now. I remember there is a natural coal mine near our Sky Fortress, but no one has mined it."
The other tutors also had their own work to do and left the classroom one after another.
The female instructor patted Xiaojie on the shoulder and said, "You did a great job."
"By the way, any news about your sister?"
After hearing these words, Xiaojie, who had been excited, gradually became serious.
He shook his head, then smiled and said, "Although there is no news, I believe that Brother Tianyang will protect my sister."
The female mentor couldn't help but sigh: "The savior who walked out of our fortress, I wonder how he is doing now."
After looking at Xiaojie again, the female teacher walked out of the classroom.
Xiaojie packed up his textbooks and just walked out of the classroom when he heard someone calling his name.
Then, a burly figure squeezed into the boy's sight.
Looking at the man's messy hair and smelling the faint smell of alcohol, Xiao Jie couldn't help but ask, "Captain Han Shu, are you drinking so early in the morning?"
Han Shu seemed to have just crawled out of bed. He grabbed Xiao Jie's hand and walked away: "Come on, come back with me."
"Your sister is back!"
The book in Xiaojie's hand immediately fell to the ground.
Sitting in Han Shu's car, Xiao Jie was still a little bit unconvinced.
He hasn't seen his sister Xun for several years since she left Skyfort.
The Kuroshio Tide broke out and disasters occurred frequently.
Although Xiaojie didn't say it on the surface, he was actually very worried about his sister.
Now I hear my sister is back.
Of course he was happy, but it also felt a little unreal.
squeak-
The tires rubbed against the road violently, making a harsh sound.
Han Shu was driving very fast, as if he was in a hurry to meet someone.
Xiaojie guessed that she wanted to see her brother-in-law.
The car door opened.
Xiaojie looked up and found that he had returned to the residence of his sister and brother.
They soon arrived at the door.
Xiaojie was a little nervous. He reached out to press the doorbell, but then pulled back.
"Press it." Han Shu encouraged.
Xiaojie then pressed the doorbell hard.
Ring-Ring-Ring-
The bell rang and soon the door opened, revealing a strange little girl.
She was about ten years old, with big eyes, long eyelashes, and looked very well-behaved and cute.
The little girl looked confused.
Then he exclaimed softly, "You must be Brother Xiaojie, Sister Xun's younger brother, right?"
Before Xiaojie could react, the little girl had already grabbed his hand and pulled him into the living room: "Sister Xun, look, brother Xiaojie is back."
The living room was surprisingly lively.
Lao Xu, Cangdu and Ji Yu are almost all here.
After his sister left, these people, like Captain Han Shu, took good care of him because of his brother-in-law Tianyang.
Especially Han Shu and Lao Xu, they came to see him almost every few days, and were happy to help if he had any difficulties.
Now, they are all here.
Old Xu was holding a chubby baby and changing the little thing's diaper skillfully. While changing, he boasted that he was the one who changed his daughter's diapers in the past, which made his daughter Xiaomai next to him very dissatisfied.
After Lao Xu changed the diaper, Xiaomai rushed to hold the baby. The little girl who had just pulled her in was very nervous. She ran over and stood beside Xiaomai, her eyes never leaving the baby.
"Xiaojie."
A familiar voice sounded.
Xiaojie looked over.
I saw Xun in the crowd and my sister.
She has basically not changed, except that her temperament is much more mature, and her whole body exudes a maternal glow.
Xiao Jie's body shook slightly, his eyes turned red, his lips trembled slightly, and finally he tried his best to control himself: "Sister, when did you come back?"
Xun came over, hugged him tightly and said, "I just got back today."
"How are you?"
"Did you eat well?"
"Let me see, you have grown taller. I almost couldn't recognize you."
Xiaojie laughed: "Of course, I grow up very fast."
He looked around: "By the way, where is Brother Tianyang?"
"He didn't come back?"
After these words came out, Xiao Jie keenly felt that the atmosphere in the room suddenly became a little solemn.