问题描述：
语法题,请帮忙分析下句子成分
The teracyclines, _______antibiotics,are used to treat infections.
A being a family
B a family of
选哪个为什么?
The teracyclines, _______antibiotics,are used to treat infections.
A being a family
B a family of
选哪个为什么?
问题解答：
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