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.