下面四幅图是制作洋葱表皮切片标本的四个基本过程，正确的顺序是（      ）。

①               ②              ③              ④　

用数学归纳法证明1+2+3+…+（3n+1）=$\frac{\left(3n+1\right)\left(3n+2\right)}{2}$，则当n=k+1时左端应在n=k的基础上加上（　　）

1947年8月，印度领导人尼赫鲁说：“今天我们结束了一个厄运的时代，印度再次发现了自己。”他的讲话是为了庆祝（    ）

选择方框内的单词，并用其适当的形式填入空白处，使内容意思通顺，语法正确。

    Linda is from ____. She is thirteen. Her sister's name is Sally. She is only five ____ old. Linda is in No.2 Middle School. She is a good student. She ____ beautiful eyes. They are big and black. She is a good football player. Her ____ star is David Beckham(大卫·贝克汉姆). Her father is a teacher. Her mother is a teacher, ____. They have a big house and a car. She has a happy family(家庭).