( )(1)当你向别人介绍海伦是你的妹妹,可以说:A. This is Helen B. Helen is my sister.
What ____________ he do? A. does B. do C. is
He is interested ____________ math. A. on B. in C. at
What's ____________ hobby? A. you B. he C. your
When ____________ your mother born? A. were B. was C. is
She was born ____________ 2012. A. in B. on C. at