题目

______ is known to us all is that the old scientist, for ______ life was hard in the past, still works very hard in his eighties. A. As; whomB. Which; whose      C. What; whom   D. It; whose   答案：C给试管里的液体加热，液体体积一般不超过试管容积的___，加热前先使试管在火焰上来回移动，这种方法叫______；为了避免伤人，加热时切记不可使试管口对着_____。