— If there are ____ trees, the air will be cleaner.— I agree. Then there will be less pollution.
-- ________ you tell me how to write it in English? -- I'm sorry, I can't.
Look! They ________ in the hallway.
Can you help me ________ my homework?
The teachers ________ on the blackboard with chalk in the future.
- ________ book is this? -- It's Mary's.