______________________________________(他从狱中逃跑的消息)frightened everyone.
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They were worried over _________________________________.(生病)
We haven't decided _______________________________________.(到哪儿去度假)
There is some doubt ___________________________.(他是否回来)
对称的N-亚硝胺类化合物主要引起(),而不对称的N-亚硝胺类化合物特别是有一甲基的亚硝胺主要引起食道癌。
A. 肺癌
B. 肝癌
C. 食道癌
D. 膀胱癌