I.：单项选择 (共20小题每小题1分，共20分)
（ ）1. I’m _______ a diet, since I put ________ weight easily.
A. in; on B. on; in C. in; in D. on; on
( )2. The headmaster ______ all the students before him, telling them to get ready for the start.
A. collected B. selected C. gathered D. elected
