如图所示,一束光斜射到平面镜上,其中反射角是( ) A.∠1 B.∠2 C.∠3

题型:选择题

问题:

如图所示,一束光斜射到平面镜上,其中反射角是(  )

A.∠1

B.∠2

C.∠3

D.∠4

考点:光的反射规律及其应用
题型:选择题

Mr. Smith has two cats. One is big and the other is small. He likes them very much. One day his good friend Mr. White comes to see him. He is very surprised(惊奇的).He finds there are two holes(洞) in the door, a big hole and a small hole. He says, “My dear friend, why are there two holes in your door?” “To let them in and out.” Mr. Black answers. “But why are there two holes?” his friend asks, “How can the big cat go through the small hole?”

小题1:Mr. Smith has _______.

A.two small cats

B.two big cats

C.a big cat and a small one

D.a cat and a bird小题2:Mr. White comes to see______. 

A.Mr. Smith

B.Mrs. Black

C.the cats

D.the holes小题3:According to this passage. _______ is not necessary(必要的).

A.The big hole

B.The small hole

C.The big door.

D.The small door.

题型:选择题

试说明市场营销近视症的主要表现和防治方法。

题型:选择题

关于使用滤线栅的注意事项,错误的是

A.使用滤线栅时要避免滤线栅反置

B.中心线应对准滤线栅中线,左右偏移不超过3cm

C.需要倾斜X线管时,倾斜方向不必与铅条方向一致

D.摄影中产生散射线较多时,可考虑选用栅比较大的滤线栅

E.使用交叉式滤线栅时,X线管不得向任何方向倾斜

题型:选择题

下列关于动物克隆的叙述,错误的是()

A.培养基中添加牛血清和胰岛素可以提高动物克隆的形成率

B.保留接触抑制的连续细胞系具有不死性但不致癌

C.无限细胞系、转化细胞系和肿瘤细胞系等容易克隆

D.将肝组织制成单细胞悬浮液后,直接培养获得肝细胞克隆

题型:选择题

采取桩柳防浪时,需在遭受冲击破坏堤坡的()顺堤线方向打设长桩一排。

A.上边缘

B.上游

C.下边缘处

D.下游

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