Put on more clothes．You ________ be feeling cold with only a shirt on．

A．should

B．would

C．could

D．must

Can you explain the ________ school yesterday?

A．absent from

B．absence from

C．absent

D．absent for

________ others say, the professor is sure that his theory is correct．

A．No matter

B．It doesn't matter

C．Whatever

D．What

It was not until 1920 ________ regular radio broadcast began．

A．while

B．which

C．that

D．since

Not until all the fish died in the river ________ how serious the pollution was．

A．did the villagers realize

B．the villagers realized

C．the villagers did realize

D．didn't the villagers realize

Not until I began to work ________ how much time I had wasted．

A．didn't I realize

B．did I realize

C．I didn't realize

D．I realized

Not until the early years of 19th century ________ what heat is．

A．man did know

B．man knew

C．didn't man know

D．did man know

It was not ________ she took off her glasses ________ I realized she was a famous film star．

A．when; that

B．until; that

C．until; when

D．when; then

It is the poisonous products ________ can cause the symptoms of the flu, such as headache and aching muscles．

A．who

B．that

C．how

D．what

It was ________ back home after the experiment．

A．not until midnight did he go

B．until midnight that he didn't go

C．not until midnight that he went

D．until midnight when he didn't go