Alice, you can _____ me at selina2001@sina.com.
The maths problems are too hard, only ______ people can work them out.
---______ does he go to Guangzhou on business? ---Three or four times a year.
I always go to the lake ____ the aftenoon, but Kate goes there ____ the night of Monday.
Jack _______ goes shopping, because he is ______ busy working.
Helen is my cousin. I often help ________ with ________ homework.