the pencil case is made of metal metal划线提问we save water (祈使句)
问题描述：
the pencil case is made of metal metal划线提问
we save water (祈使句)
答
What is the pencil-case made of?
Let's save water.
答
What is the pencil case made of?
Save Water.
答
What is the pencil case made of?
Save water. / Let's save water.