___ the beginning of the meeting, the president made a speech ___ how to reduce pollution.
| A．at; in | B．at; on | C．in; on | D．on; on |
----What do you do after class?
-----Sometimes, I talk __________ my friends.
A. in B. of C. to
Would you like _________ to music?
A. listen B. to listen C. listening
Seven _________ workers work in that factory.
A. thousands of B. thousands C. thousand
There are many _________ on the table.
A. potato B. water C. potatoes
His father is ________ English teacher in Liuzhou.
A. a B. an C. the