We usually go to work _____ subway. [ ]
A. by the
B. by a
C. by
D. on
答案:C
构成蛋白质的最基本单位是氨基酸。( )
阻力系数和升力系数比值达到最小对应的点是()
A.在失速速度VS处
B.升力系数曲线的最高点
C.从原点引阻力曲线的切线,切点对应的点