圆锥形烟囱帽的底面直径为80cm，母线长为50cm，则这样的烟囱帽的侧面积是（  ）．

People usually____in some western countries when they see each other．

秋天到了，请你以秋天为话题，写一篇短文。题目自拟。

提示：①题目可以是“__的秋天”（可以填：美丽、多彩等）也可以是“秋天的__”（可以填：雨、落叶、色彩、校园、田野、早晨等）。②描写景物要突出季节特点，层次要清楚，按照一定的写作顺序来组织材料。

（400字左右）

阅读短文，从各题所给的选项中选择最佳选项。    

    It was Friday night and Marty was relaxing in a chair. His mom was washing the dishesin the kitchen. But before she could finish, 1 didn't feel well and had to stop. She said she would do it after a  2  .

    "Are you OK, mom?" asked Marty.

    His mom said, "Yes, I'm fine. But I need to rest." Then she went to 3  .

    Marty felt a little 4 . He knew he should help his mom more.   5 when his mother rested, he 6 all the dishes and cleaned the kitchen. The kitchen was very clean and Marty felt much better.

    When Marty's mom woke up, she thought she had  7 to do. She had to clean the kitchen and wash all the dishes. But when she went to the kitchen, she could not believe her  8  . The kitchen was so clean. She  9 Marty for all his work. She told him he was a really nice boy.

    On that day, Marty learned that 10 others makes everyone happy. It makes others feel happy, and it makes you happy, too.