1 . The man was observed ________ into the house and help himself to what he liked before the owner came back.

A．slip

B．to slip

C．slipping

D．slipped

2 . Mary became a baker at age 14, because her grandfather paid the local baker ________ her all the skills.

A．to have taught

B．to teach

C．teaching

D．having taught

3 . That approach brought Cobb’s air travel last year down by 75%, and she plans ________ (continue) the practice. “It has been fairly rewarding.” she says, “a really positive change.” (所给词的适当形式填空)

7 . According to the scientists, the little polar bear will be the first ________ the extreme cold.

A．to survive

B．surviving

C．to be surviving

D．survived