He ________ the classroom a moment ago .

[　　]

This is a new house which ________ in .

[　　]

Heat butter in the frying pan (煎锅) ________ .

[　　]

A．until melted

B．until melting

C．while melting

________, land may not be ruined.

[　　]

A．When giving proper care

B．Unless giving proper care

C．Given proper care

He locked the door , ________ .

[　　]

A．thus made sure no one would interrupt (打断) him

B．thus making sure no one would interrupt him

C．though made sure no one would interrupt him

________ , he had an accident on the icy road .

[　　]

A．Although driving carefully

B．Even though drove carefully

C．Though driven carefully

________ , we stopped to look at the map .

[　　]

A．Knowing not which road to take

B．Not knowing which road to take

C．Not knew which road to take

________ , we forgot our one o'clock class .

[　　]

A．Absorbing in our conversation

B．Though absorbed in our conversation

C．Absorbed in our conversation

The children stood on the pavement , ________ .

[　　]

A．watching the buses coming and going

B．watched the buses coming and going

C．when watched the buses coming and going

________ , the spaceman saw the Great Wall of China .

[　　]

A．While flew in the spaceship

B．While flying in the spaceship

C．If flew in the spaceship