句子单数变复数，注意以下五要素

(1).主格人称代词要变成相应的复数主格人称代词,即I→we, you→you,she,he,it→ they。如:

She is a girl. →They are girls.

(2).am,is要变为are。如:

I’m a student. →We are students.

(3).不定冠词a,an要去掉。如:

He is a boy. →They are boys.

(4).普通单数名词要变为复数形式。如:

It is an apple. →They are apples.

(5).指示代词this,that要变为these,those。如:

This is a box. →These are boxes.