轴电流有什么危害？

下部固定绳距接触线距离正线为（）mm，侧线为300mm，允许偏差±50mm。

A、250

B、400

C、700

D、800

发电机推力轴承高压油顶起装置的作用是什么？

Good Table Manners Manners play an important part in making a favorable impression at the dinner table. Here are some general rules： Napkin （餐巾） use The meal begins when the host unfolds his or her napkin. This is your signal to do the same， so place your napkin on your lap. Unfold it completely if it is a small napkin. Or in half， lengthwise （纵向地） ，if it is a large dinner napkin. If you need to leave the table during the meal， place your napkin on your chair as a signal to your server that you will be returning. Once the meal is over， place your napkin neatly on the table to the right of your dinner plate. Do not refold it. Use a napkin only for your mouth. Never use it for your nose， face or forehead. Use of utensils （餐具） Start with the knife， fork or spoon furthest from your plate， and work your way in， using one utensil for each course. If soup is served， remember to spoon away from yourself. This helps stop the drips. Do not put the entire soup spoon in your mouth. Instead， fill a soup spoon about 75 per cent with soup， and sip（啜饮）it from the side noiselessly. After finishing dinner， place the knife and fork parallel to one another across the plate with the knife blade facing inward toward the plate. Using your fingers Here's a list of finger foods： sandwiches， cookies， small fruits or berries with stems， French fries and potato chips， and hamburgers. Chew（咀嚼）with your mouth closed and don't make noise； don't talk with your mouth full. Bread must be broken with your hands. It is never cut with a knife. Don't pick something Out of your teeth. Instead， excuse yourself to the bathroom. If possible， try not to cough at the table. Do not put your elbows （肘） on the table. In France， it is essential to have both hands above the table at the same time. Do not put bones or anything else on the table. Things that are not eaten should be put on your plate.All of the following are finger foods EXCEPT（）.

A、soup

B、sandwiches

C、cookies

D、hamburgers

隔离开关、负荷开关刀闸合闸时，刀闸水平，两闸刀中心线吻合，允许偏差（）mm。

A、2

B、3

C、4

D、5

水轮发电机主轴有何作用？