问题 选择题

让显微镜镜筒下降时,眼睛应注视(  )

A.目镜

B.物镜

C.镜筒

D.准焦螺旋

答案

使用显微镜时,可以分为取镜安放、对光、观察和整理四步.对光完成后,要先将玻片标本放在载物台上,标本要正对通光孔.然后转到粗准焦螺旋下降镜筒,这时眼睛要看着物镜,以免物镜碰破玻片标本.

故选:B

综合

读“世界人口分布图”,回答下列问题。

(1)世界人口最稠密的四个地区是:                                                                                               等。

(2)图中A、B、C、D四地,人口稀少的原因是:

    A                                                                                                                                                        

    B                                                                                                                                                         

    C                                                                                                                                                         

    D                                                                                                                                                         

(3)亚洲、非洲和拉丁美洲国家人口增长较快,产生的问题是                                                               

                                                                                                  ,解决的措施是                            。 

单项选择题