我国各民族的分布特征是（    ）

升入初中后的小明最近遇到了以下问题：
1.同学们在热烈的讨论元旦晚会的事，他也想谈谈自己的见解，但又怕说出来被大家取笑。
2.他和同学约好星期天出去玩，但妈妈说现在外面坏人多，不让小明出去。
3.最近小明发现前排女生的形象最近老师出现在脑海中，以至于上课经常走神。

现有一个圆心角为90°，半径为10的扇形纸片，用它恰好卷成一个圆锥的侧面（接缝忽略不计），则该圆锥的底面半径为（         ）

根据首字母提示补全单词。

A

    Shanghai's Maglev Train(磁悬浮列车) runs from Longyang to Pudong International Airport(国际机场). The whole trip takes about 8 minutes.

    Children at or under 120 cm tall don't need to buy tickets to take the train, but they cannot take the train by themselves. Children above 124 cm must buy a full-price ticket.

    If you buy a round ticket, you can get on the train at Longyang Road Station or Pudong Airport Station, and get off at the other station. The return part of the ticket must be used on the same day.