题干
. It is reported that two hotels，_____ are being built in my hometown，will open next year.
A：they both
B：which both
C：both of them
D：of which both
答案(点此获取答案解析）
D
上的函数
满足
，且
， 
，若有穷数列
（
）的前
项和等于
，则n等于