It _____ me about 20 minutes to finish that work.[ ]
A. spent
B. cost
C. paid
D. took
答案:D
若A是单项式,且A(4x2y3+3xy2)=-12x3y5-9x2y4,则A2=______.
肱骨滑车位于()。
A.肱骨上端前面
B.肱骨下端内侧
C.桡骨上端
D.尺骨下端