题干
There are a few _______ magazines in my home.
A：copy of
B：copies of
C：copys
D：copies
答案(点此获取答案解析）
B
There are a few _______ magazines in my home.
A：copy of
B：copies of
C：copys
D：copies
的通项公式是
，若前n项和为
则n等于 （ ）