如图所示是一个横截面为半圆、半径为R的光滑柱面，一根不可伸长的细线两端分别系住物

阅读理解

                                                        You are what you eat

     Keeping better eating habits can help you reduce (减少) disease. A healthy eating plan means

choosing the right foods to eat and preparing foods in a healthy way.

                                                   _______________________

     Do you often change your toothbrush? Maybe you think it is not necessary. A study shows old

toothbrushes bring disease. You should often change your toothbrush.

                                                                  Exercise

     Swimming, running, skating, skiing, dancing, walking and some other activities can help you stay

healthy. You should exercise at least three times a week and for twenty minutes or more each time. Do it.

                                                          Plan out your life

     You should have breakfast before you go to school. Have a proper (合适的) meal for lunch. Follow

a healthy diet.

1.What's the passage mainly about?

A.Healthy food.

B.Healthy lifestyle (生活方式).

C.Junk food.

D.Healthy sports.

2.What is the best title (标题) for the second paragraph?

A.Man's disease

B.Disease

C.Watch the toothbrush

D.Your bathroom

3.At least how long should you exercise each time?

A.Twenty minutes.

B.Fifteen minutes.

C.Five minutes.

D.Ten minutes.

4.From the passage, we know _______ can help us stay healthy.

A.proper diet

B.exercise

C.sleep and exercise

D.proper diet and exercise

5.What does a healthy eating plan mean?

A.Choosing the right foods.

B.Cooking the foods in a healthy way.

C.Never eat meat or fresh vegetables.

D.Both A and B.

地球到太阳的距离为150000000km,将150000000km用科学记数法表示为_______▲______km.

原子能就是核能，利用原子能发电的工厂称为核电站。[ ]

以下哪项不是调试光功率的目的（）。

A.OSNR符合要求

B.单波光功率均衡

C.减少对无源器件的损伤

D.避免非线性效应

0.2～0.5μg/ml氯用于

A．温度计消毒
B．自来水消毒
C．空气消毒
D．新生儿滴眼预防淋病奈瑟菌感染
E．排泄物消毒