2 . In our school there are 50 students, half of __________ wear glasses. （用适当的词填空）

3 . Elon Musk has founded many high-tech companies, almost half of ________are expected to direct tomorrow’s world. (用适当的词填空)

5 . I'd like to thank Professor Smith, without       help I would never got this far.

A．his

B．whose

C．which

D．whom

6 . They thanked Tom, without __________ they wouldn’t have succeeded.(用适当的词填空)

7 . Recently, parts of our province have been struck by severe flood, from ______ effects the people are still suffering. (用适当的词填空)

8 . The science of medicine, _________which we owe a great deal, is perhaps the most important of all the branches of science. (用适当的词填空)

9 . There are many clowns in the playground, some of ________ are performing opera. (用适当的词填空)

10 . Many lessons are now available online, from ___________students can choose for free. (用适当的词填空)