单选题The number of vehicles has been steadily increasing. _______, more than 100 cities in the United States still have levels of carbon monoxide that exceed legally established limits.
单选题Washington Roebling was a cripple ______ he lived.
单选题A biologist does not merely describe organisms, but tries to learn __ act as they do.
单选题What controls the migration of birds seems to be ____.
单选题"Has he come back? .... Yes, he __ back for three days.
单选题What you have done is ______ doctor’s orders.
单选题Sometimes even the smallest thing will upset an __ person.
单选题If all the continents and mountains were bulldozed fiat, the earth __ by water more than 12,000 feet deep.
单选题The news _______ heard everywhere.
单选题The clerk asked Robey __ later in the day.
单选题The police __ the records of all those involved in the crime.
单选题The peasants __ their land.
单选题__, he had to leave school.
单选题__ nothing more to discuss, the CEO got to his feet, said goodbye and left the meeting room.
单选题With winter here you can these skirts till you need them again next summer.
单选题I need __ more volunteers to help clean the classroom.
单选题Most scientists agree _______ was hot for at least a time.
单选题Gorillas are quiet animals, _______ they are able to make about twenty different sounds.
单选题_______ he was a regular customer, the boss allowed 10% discount off the prices of the goods.
单选题He was ______ by the external examiner.