内燃机根据其将热能转化为机械能的主要构件的形式,可分为活塞式内燃机和()两大类。
参考答案:燃气轮机
It worries him a lot that ______ little money he earns in the company can hardly support so large ______ family.
A.不填;the
B.a; the
C.a; 不填
D.the; a
形成迟到波的原因是由于波的传播方向改变而增加声程所引起的。