普通硅酸盐水泥强度等级不包括（）。 A.32.5 B.42.5 C.52.5

(12分）如图，将质量m＝2kg的圆环套在与水平面成θ=37°角的足够长直杆上，直杆固定不动，环的直径略大于杆的截面直径，杆上依次有三点A.、B、C，s_A.B=8m，s_BC=0.6m，环与杆间动摩擦因数m＝0.5，对环施加一个与杆成37°斜向上的拉力F，使环从A.点由静止开始沿杆向上运动，已知t=4s时环到达B点。试求：（重力加速度g=l0m/s²，sin37°=0.6，cos37°=0.8）

（1）F的大小；

（2）若到达B点时撤去力F，则环到达C点所用的时间。

患者，男，36岁，因半年来右下第一磨牙咬合面深龋洞不能咬物而就诊。1周前已做一次垫底银汞充填，1天前出现自发痛，冷热痛持续，不能咬物。查：右下第一磨牙咬合面充填体完整，叩痛（+），冷测引起剧痛。

其原因最可能为（）

A.备洞对牙髓刺激

B.充填时垫底不良

C.充填后电流作用

D.充填前诊断错误

E.充填材料的刺激

甲是间歇性精神病人。某日甲精神正常时喝醉了酒，把某酒店老板打成重伤，则甲（）。

A.应当负刑事责任，但可以减轻处罚

B.应当负刑事责任，但可以从轻处罚

C.不负刑事责任，因其是精神病人

D.应当负刑事责任

The following questions present a sentence, part of which or all of which is underlined. Beneath the sentence you will find five ways of phrasing the underlined part. The first of these repeats the original; the other four are different. If you think the original is best, choose the first answer; otherwise choose one of the others.

These questions test correctness and effectiveness of expression. In choosing your answer, follow the requirements of standard written English; that is, pay attention to grammar, choice of words, and sentence construction. Choose the answer that produces the most effective sentence; this answer should be clear and exact, without awkwardness, ambiguity, redundancy, or grammatical error.

His opponent having sprained his wrist, Andrew could have won by exploiting this weakness, but he chose not to do it.（）

A. His opponent having sprained his wrist, Andrew could have won by exploiting this weakness, but he chose not to do it.

B. Andrew could have won by exploiting this weakness after his opponent sprained his wrist, but he chose not to do so.

C. Choosing not to do so, Andrew could have won after his opponent sprained his wrist by exploiting this weakness.

D. After his opponent sprained his wrist, Andrew could have won by exploiting this weakness, but he chose not to do so.

E. After his opponent sprained his wrist, Andrew could have, but chose not to do it, won by exploiting this weakness.

摩擦力的方向与物体运动方向相反。