如果劳动力的供给曲线是（）的，税收对劳动投入的影响表现为收入效应。
A.向右上方倾斜
B.向后弯曲
C.水平
D.向右下方倾斜
参考答案：B
— I remember you were a talented pianist at college. Can you play the piano for me?
— Sorry, I ________ the piano for years.[ ]
A. don't play
B. wasn't playing
C. haven't played
D. hadn't played
长度的法定计量单位是米（m）及米的常用倍数、分数单位，（）表示毫米。
A、km
B、cm
C、mm
D、μm
