下列关于电与磁的说法中正确的是（　　）

读下列材料，回答下列问题。

材料一：月球基本概况：月球质量约为地球的 $\frac{1}{81}$ ；体积只有地球的 $\frac{1}{49}$ ；月球表面的引力也只有地球表面的 $\frac{1}{6}$ 。月球表面基本上没有大气，月面温度差可以达到300℃以上。月球表面由岩石碎屑和尘埃组成的风化层(月壤)所覆盖，一般厚5~10m，富集的化学元素有H、He、N、C等，初步估算全月球月壤中3He的资源量可达100万~500万吨，3He是人类未来可长期使用、清洁、安全而廉价的可控核聚变燃料。组成月球和地球的化学元素相同，月岩中发现的100多种矿物中绝大多数也与地球的矿物相同，只有静海石等5种矿物在地球上未发现过。月球表面没有水体，而月球南北两极的月壤中存在大约66亿吨的水冰。它们是彗星撞击后残留下来的。

材料二：地月系示意图，图中箭头为地球自转方向。

根据短文内容，完成下面的任务。

Dear Grandma,

    How are you? I am very busy this month. (A)September 5th is my good friend Gina's birthday. I will go to her birthday party in the evening. On the eleventh, (B)我有一个英语测试. On September 17th, I have a baseball game. You know I love baseball. On the 24th, I have a school trip. On the 28th, I'll go to Mr. Cool's Clothes Store. The clothes there are on sale that day. I want to buy a pair of sports shoes and a T-shirt. The hats there are very nice. I will buy one ① ________ you. Oh, Grandma, I'm very sorry I can't go to see you ② ________ my parents this month. See you next month.

 Yours,

Eric