Little Jim sat under the tree, ___ about that maths problem.
| A．to think | B．and thinks | C．thought | D．thinking |
—Where is Tom ?
—Well , he you here . Otherwise he would come down right now .
| A．didn’t know ; were | B．hasn’t known ; are | C．doesn’t know ; are | D．hadn’t known ; were |
All of the guests by 9 o’clock , but the host until 15 minutes later .
| A．arrived ; didn’t turn up | B．had arrived ; didn’t turn up |
| C．arrived ; hadn’t turned up | D．had arrived; hadn’t turned up |
Mike didn’t notice Alice entering his room. He ____ a phone call.
| A．answered | B．has answered | C．was answering | D．is answering |
—Did you find the missing couple in the mountain yesterday?
—No, but we ________ to get in touch with them ever since.
| A．have tried | B．have been trying |
| C．had tried | D．had been trying |
—Such a mistake could have been avoided.
—Unfortunately, he _______ the mistake again and again.
| A．repeated | B．would repeat |
| C．had repeated | D．would have repeated |