下列共价化合物中，哪些是以极性键结合的（ ）
（1）F2 （2）O2 （3）NH3 （4）CH4 （5）SO2
A．（1）（2）
B．（1）（2）（4）
C．（3）（4）（5）
D．（2）（3）（5）
C
F2分子和O2分子中，成键原子相同，它们是以非极性键结合的——备选项中有（1）或（2）都不可选，A、B、D被排除，答案为C。
NH3、CH4、SO2分子中，成键原子互不相同，它们是以极性键结合的。
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