问题集合

The important advantage of a cell phone is to use anywhere.
如果advantege改成复数，那么是用is还是are？why？
回答：用are，既然是可数名词的复数，当然用are

He has been in bejing for a year.
It has been a year since he went to bejing.

advantages are
It has been, since

补充一点题外的。
to use anywhere
to use这样用不太好。要表达的意思应该是
The important advantage of a cell phone is you can use it anywhere.
or The important advantage of a cell phone is that it can be used anywhere.

用are因为后面to use anywhere补充说明的是手机的优势！不是手机！而advantage加了s就变为负数，它是可数名词，所以应该用are
It has been，since