He drew a handkerchief from his overcoat pocket.

    Welcome to our club l Our club is a good place to have fun for students. We have ten sports teachers and five art teachers. Here you can learn to play tennis and you can learn to draw（画画）.And we have many great activities. October is a busy month. On October 5th,we have a trip in the morning. And on October 20th,we have two games, a tennis game and a baseball game. Your parents can come to the club to watch the games. On December 18t",we have a music festival. It's very interesting. And on December 23nd,we have an English party.

    In the club, we have a food store. You can have lunch or dinner here. Come and have a good time here !

如图，两个完全相同的空心塑料球A和B，用两根完全相同的绝缘丝线将两球悬挂在天花板上的一点，当M、N两处都带上适量负电后，A，B两球“恰好接触而不挤压对方”．请画出B球受力示意图．