I can still remember that it is since the 1990’s, _____ we began to use cell phones,_______ the number of mobile users has greatly increased．
| A．while; when | B．when; what | C．before; that | D．when; that |
.This summer she took a training course, which was to help people develop their reading skills.
| A．operated | B．devoted | C．designed | D．furnished |
the large amount of time devoted to playing the piano, she doesn’t play well enough.
| A．Because | B．Since | C．Despite | D．With |
.Our chemistry teacher announced that he would do the experiment in a different way
we might find interesting.
| A．which | B．in which | C．in that | D．whom |
While she is a lovely girl, she be extremely difficult to work with.
| A．may | B．must | C．should | D．can |
A dictionary is necessary if you want to learn English, so you’d better buy .
| A．this | B．that | C．it | D．one |