A:a
B:b
C:c
D:d
阅读理解 Tom and his father, Mr. Smith, always go out for a walk after supper every day. After that, he does his homework and watches TV for half an hour. Then he goes to bed. Now Tom and his father are taking a walk along the road. It begins to rain. Tom wants to run for home. But his father says very slowly, “Don't run. Isn't it raining in front of you?”
由江淮汽车公司自主研发和量产的、荣获“中国心”十佳发动机称号的VVT发动机,在国内处于领先水平、在国际处于先进水平.VVT发动机工作时,____冲程使汽车获得了动力;若VVT发动机的能量流向如图所示,则热机效率是____.
一个五位自然数a1a2a3a4a5-------,ai∈0,1,2,3,4,5,i=1,2,3,4,5当且仅当a1>a2>a3,a3<a4<a5时称为“凹数”(如32014,53134等),则满足条件的五位自然数中“凹数”的个数为( )