下列叙述中正确的是() A . 在中,Cu为配位原子,NH3为配体 B . 冰分子内氢氧原子间以共价键形成的晶体中,每个水分子周围有4个紧邻的水分子 C . HI的相对分子质量大于HF,所以HI的沸点高于HF D . CaO2和CaH2均是含有共价键的离子晶体 答案:B
Tom's father is seriously ill, ________ is exactly ________he is worried about.
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A.which; that
B.that; what
C.what; which
D.which; what