More and more people choose to shop in a supermarket as it offers a great ________ of goods．

expression

mixture

variety

combination

Many British people have noticed that butterflies ________ from its natural habitats during the past several years．

are disappearing

have been disappeared

have been disappearing

will have disappeared

At the routine office meeting, the headmaster insisted that the problems ________ paid special attention to．

referred to being

referred to be

refer to being

refer to be

With many major economic problems ________ to be solved, there is no point predicting the growth rate of this year now．

remaining

remained

have remained

having remained

Everybody's fingerprints are ________, so the police can easily find the thieves if any is left when they're stealing．

single

particular

special

unique

She hesitated at the gate of the canteen, ________ whether to enter or not．

to wonder

wondered

wondering

wonder

I met one of my students the other day．After several years, she changed a lot and looked different from ________ she used to be．

that

whom

what

who

________ the program, they have to stay there for another two weeks．．

Not completing

Not completed

Not having completed

Having not completed

I shall never forget those years ________ I studied in the school with my classmates and teachers， ________ has a great effect on my life．

that; which

when; which

which; that

when; who

The computer system ________ suddenly while he was searching for information on the Internet．

broke up

broke into

broke out

broke down