Bob called to tell his mother that he couldn’t enter the house, for he ________ his key at school.
A. had left B. would leave
C. was leaving D. has left
It was only after he had read the papers _____Mr. Gross realized the task before him was extremely difficult to complete.
A. when B. that C. which D. what
When I arrived, Bryan took me to see the house，_____ I would be staying.
A. what B. when C. where D. Which
_______ more and more people speak the global languages of English,
Chinese, Spanish, and Arabic, other languages are rapidly disappearing.
A. When B. While
C. As D. As soon as
A small plane crashed into a hillside five miles east of the city, _____all four people on board.
A. killed B. killing
C. kills D. to kill
Since___1980s, the new technology has been used on trains in _____Europe.
A. the ; the B. / ; the
C. the ; / D. / ; /
