1:it's best to come to china in spring.等于：三空 to come to chin

1:it's best to come to china in spring.=(the best time) to come to china is in spring.
最好在春天去中国=去中国的最佳时候是春天
2：He runs fastest in his class.= (None runs) faster than he in his class
他在班级里是跑得最快的=在班里没人比他跑得更快 ,题目中的第二个“fastest"应改为"faster"才对,因为比较级才接than
再问： 你好，请问第2题中为什么不用noboby runs.
再答： 哦，none 与nobody 都是”没有人“的意思，这里可以互换