用螺丝固定工件时，要在螺帽下垫一个面积较大的垫圈，使用垫圈是

【名词&注释】

过去式(past tense)

[单选题]用螺丝固定工件时，要在螺帽下垫一个面积较大的垫圈，使用垫圈是为了 【 】

A. 增大螺帽对工件的压强
B. 减小螺帽对工件的压力
C. 增大接触面的粗糙程度，防滑
D. 增大工件受力面积，减小压强

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[单选题]（ ）30． Many families were affected because of ________ ．

A. the heavy rain on Monday
B. the broken banks of the river
C. the floods across Mexico
D. the death of 132 people

[单选题]AMany children feel that the most important people in their lives are their friends．They be- lieve that their family members don-t know them as well as their friends． In large families， it is quite often for brothers and sisters to fight with each other and then they can only go to their friends for some ideas．

A. Even when they are not with their friends， they usually spend a lot of time talking on the phone with their friends．This communication is very important to children’s growth， because friends can discuss some-thing， but it's difficult to discuss it with family members． However， most parents like to choose friends for their children Some parents even don-t allow their children to meet their good friends．
B. Who chooses your friends? What do your parents think of your friends?
D. Many children think ________ can understand them better．
E. friends
F. brothers
G. teachers
H. parents

[单选题]20． The car is running _______' It seems to be flying．

A. more and faster
B. faster and more
C. fast and fast
D. faster and faster

[单选题]The ducks ___________ many eggs last week．

A. lay
B. laid
C. lied
D. werelaid

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