Before graduating from university in 2023, Lin Xing had experienced this kind of time travel three times. Judging from these limited three experiences, he believed that the length of time he traveled back to the past should be related to the size of the danger.,But even when class time had passed, there was still no one else in the classroom besides him. Not even the school bell rang.,“I don't know, we’ve sealed off the perimeter. Who knows how he got in…”。