题目

 Radium salts, which have been found to _____ in bones, give rise to cancers of the bone. A. pile up    B. build up    C. keep up    D. pull up   答案：B今年是我国农历的马年，下列对马的特征叙述中，正确的一组是（　　）①用肺呼吸②胎生、哺乳③体表被毛④心脏四腔⑤变温动物⑥体内有膈． A、①②③④⑤B、①②③④⑥C、①③④⑤⑥D、①②③⑤⑥