The boy on the playground ____ be Tom, because he saw him in the library just now.
I first met Lisa three years ago. She ________ at a radio shop at the time.
. As a volunteer, he often goes to the hospital to ________ the sick.
_______ of the students will take part in the sports meeting.
Trees and flowers ________every year to make our country more beautiful.
—Mr. Smith, would you please speak a little more ________?—Sorry! I thought you could follow me.