1 . Recently it has been noticed _____ an increasing number of students are bringing smartphones to school, _____ means using smartphones reasonably has become _____ unavoidable topic for us students.

A．/; that; a

B．that; which; an

C．/; which; an

D．that; which; the

2 . China will allow all couples to have three children, ________, in my opinion, is helpful to cope with the increasingly aging society.

A．that

B．which

C．what

D．who

3 . During my stay in America, I lived in university accommodation with other international students, ________ allows me to meet people from diverse cultural backgrounds.

A．who

B．what

C．which

D．that

4 . These days, teachers have been sparing no efforts to create         they hope will be the best means to improve the efficiency of online teaching,         some students don’t notice or care about, though.

A．that, which

B．what, which

C．which, what

D．what, that

5 . It was in 1999________emojis were first introduced in Japan,________helps people express their feelings.

A．which; that

B．when;who

C．that; which

D．what; where