汽油机怠速不良有哪三种现象？其原因是什么？

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。
How to keep healthy? It’s easy for us to catch a cold in winter and spring because the weather changes a lot in spring and it is too cold in winter. But if we take care in our life, all of us can keep healthy without any cold.
    1    . This will stop germs（细菌,病毒） passing from one person to another. When you finish your work or before you eat, you’d better wash your hands.
    2     . Use a tissue（纸巾）, and then throw it into dustbins at once. When others around you are coughing, I advise you to turn your head away from the people so that their viruses won’t reach you.
Get more fresh air. Germs like staying around in dry and warm rooms.    3    . Don’t stay too long in the places with too many people.
If flu is going round house or school, you should try to stay away from those who are ill.    4   
Boil your toothbrush for about a minute. This kills germs .   5      . If you have used the toothbrush for three months or so, throw it away and buy a new one.

A. Have a shower every day B. Wash your hands often C. Don’t use your hands when coughing   D. Don’t go out often when you are coughing E. Besides, don’t use the same toothbrush too long F. In this way, you won’t be infected by these people G. you’d better stay in the places with more fresh air