问题描述：
最好帮忙解答下为什么这样选``
1.Planting a tree is_______.Trees help control pollution.
A fun B a fun C great funs
2.My mother's birthday is ________ of August.
A at the seventh B in the seventh C on the seventh
1.Planting a tree is_______.Trees help control pollution.
A fun B a fun C great funs
2.My mother's birthday is ________ of August.
A at the seventh B in the seventh C on the seventh
问题解答：
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