近代有一位思想家主张学习西方,在其著作中提出了“物竞天择,适者生存”的观点。这位思想家是[ ]
A.詹天佑
B.严复
C.魏源
D.郭沫若
答案:B
There is a big library in our school.There are more than twice________five years ago. [ ]
A. books than
B. as many books as
C. many books as
D. many more books than
一个质量为m的小球从高处由静止释放,不计空气阻力,当小球下落高度h时,重力的瞬时功率为[ ]
A.
B.
C.
D.