判断“链式队列为空”的条件是______(front为头指针，rear为尾指针)。A

Why do we need to throw less away? There are two reasons. One is that some resources（资源）are nonrenewable（不可再生的）. That means there is only a certain amount of that resource in the world. One example of these resources is oil. When we use up all the oil in the world, there will be no more.
There is a second reason for throwing less away. All of our trash has to be put somewhere. Often, it is put into garbage dumps（垃圾场）. Much of that trash will be there for hundreds of years. The dumps ill be filled up with all this trash.
There are three ways to cut down on trash.
One way is to recycle. When you recycle something, it means it is made into another shape and used again. Old newspapers may become paper bags. A glassware can be melted（熔化）and made into a bottle.
Another way to cut down on trash is to reuse things. You can wash and use a bottle again that can hold mustard（芥末酱）or something else.
The third way to cut down on trash is to reduce the amount of trash you make, for example, stopping buying things that you don’t need in the first place. That reduces the amount of the earth’s resources.
任务型阅读：根据文章内容填写下面表格。（10分）

Reasons for throwing less away	Some resources are 1            .
	The 2          will be filled up with all this trash.
	To 3           something.
Ways to cut down on trash	To 4           things.
	To 5           the amount of trash you make.