In those days, the old woman ________ sit at the door for hours, waiting for her son to return from abroad. [ ]

A. should

B. used to

C. might

D. would

在短时记忆中，一遍遍地机械地重复识记材料是（ ）。

A．有效复述

B．无效复述

C．精细复述

D．保持性复述