It's quite normal to ________ ten percent of the cost of a building for a period of six months or so, in case faults are found in it.
A.keep up
B.keep away
C.keep off
D.keep back
网友回答
D解析此题考查短语动词的用法。keep up意为“保持、继续”；keep off意为“避开、远离”；keep away意为“摆脱”，皆与句意不符。只有D项符合题意，意为“克扣、留下”。