They ______ by the curious way their cigarettes burned and tested.

[    ]

A. were puzzling   B. puzzling   C. were puzzled   D. puzzled

The fire service began to wonder _______ the fire was caused by cigarette ends that people carelessly threw away.

[    ]

A. that   B. what   C. which   D. whether

The important point to remember is ______ you need a short lesson before starting to work with the machine.

[    ]

A. that   B. what   C. which   D. how

The noise I had heard ______ by the arrival of the car.

[    ]

A. caused   B. is caused   C. are caused   D. was caused

The machines ______ we use to make copies are called photocopies.

[    ]

A. that   B. what   C. where   D. when

He left the answering machine on ______ people could leave a message when there was nobody in the office.

[    ]

A. so   B. so that   C. in order   D. in order to

By the time the course ends, ________ a lot about American history.

[　　]

By the time I got to the bus stop, the first bus ________.

[　　]

-“When are you going to give a talk on English grammar?”

-“I _______ on that already.”

[　　]

Mr. Hawthorn spent the weekend in the country as he ________ to the office on Saturday.

[　　]