在某个容量为300的样本频率分布直方图中，共有9个小长方形，若中间一个小长方形的面积等于其他8个小长方形的面积和的$\frac{1}{5}$，则中间一组的频数为（  ）

阅读理解，根据材料内容选择最佳答案。
    The Macintosh family is in England. Mr. Macintosh is a farmer(农场主). He has three people help him on the farm. They help him look after the animals(照顾动物). Mrs. Macintosh is a teacher. She teaches math. She can play the piano and the guitar. Mr. and Mrs. Macintosh have one son and one daughter. Their son's name is Tom and their daughter's name is Fiona. Tom and Fiona like music very much. Tom can play the guitar and his sister, Fiona, can play the piano. Tom and Fiona go to the school music club every Wednesday. Next month they will play for all the teachers and students in their school. Mrs. Macintosh is very happy for them. Mr. Macintosh can't play the guitar or the piano but he can sing. Sometimes, the family plays and sings together(在一起) after dinner in the evening. That's Mr. Macintosh's favorite family activity(活动).

2010年4月2日，姚明入股的北京合众思壮科技股份有限公司（以下简称合众思壮）在中小板正式上市。据此回答问题。
【小题1】合众思壮以85．01元开盘，高开高走，收市时升幅较发行价上涨近150％。材料表明（   ）

A．股票是高收益、高风险同在的投资方式

B．股票价格的波动具有不确定性

C．合众思壮的发展前景得到了投资者的肯定

D．股东不可以要求公司返还本金

【小题2】根据合众思壮招股书显示，姚明在2007年12月18日签订《股权转让协议》时的认缴出资额是37．5万元，姚明在短短两年间，投资收益率高达近百倍。姚明的投资收益属于（   ）
①按技术要素获得的收人 ②按资本要素获得的收入
③合法的劳动收入       ④合法的非劳动收人

已知函数，正项等比数列满足，则等于（ ）

已知点A（﹣3，0），B（0，3），若点P在圆x²+y²﹣2x=0上运动，则△PAB面积的最小值为____