(单选题)31: 硝酸分子中有一个π键，可表示为
A:
B:
C:
D:
E:
1.(text)I.VocabularySkills（2points）Whichofthewordsbelowcontainaprefixwithanega...
1.(匹配题)I.Vocabularyskills（3points） Lookatthecolumnsbelow.Matcheachvocabular...
1.(完形填空题)1．ListentotheconversationanddecidewhetherthefollowingisT(true)orF...
1.(完形填空题)1．ListentotheconversationanddecidewhetherthefollowingisTrue(T)orF...
1.(完形填空题)1．ListentotheconversationanddecidewhetherthefollowingisTrue(T)orF...
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