汽油机的缸径一般较小，因为过大会使（）加长，而（）时间增长，从而产生（）。
参考答案：火焰传播距离；自燃准备；爆震
My brother with his friends tomorrow if it . [ ]
A. is going to hike; won't rain
B. is going hiking; doesn't rain
C. will go hiking; won't rain
D. goes hiking; doesn't rain
不属于髓母细胞瘤病理特点的是（）
A、恶性程度高
B、属于胚胎性肿瘤
C、多发于小脑蚓部
D、易出现坏死
E、可沿脑脊液播散
