起草单位应当于规范性文件有效期届满前（）内进行评估。
A.6个月
B.3个月
C.2个月
D.1个月
参考答案：A
受精是指 [ ]
A．产生卵细胞的过程
B．产生精子的过程
C．精子和卵细胞结合的过程
D．胚胎发育的过程
We thought of selling this old furniture, but we've decided to _______ it. It might be valuable. [ ]
A. hold on to
B. keep up with
C. turn to
D. look after
