闪点越高，引起火灾爆炸的危险性越大。
参考答案：错
栽800株西瓜苗，因为霜冻只有160株成活，则西瓜苗的成活率是______．
How did all these _________?[ ]
A. came out
B. come up
C. come across
D. come about
