(2013·重庆高考)Recycling is one way to protect the environment; reusing is ________.

There are lots of flowers on ______ sides of the street.

—Who helped Jessie with her English?—_______, she taught herself.

——With 4G mobile phones, people can even see each other as they talk.  ——Really? Would you show me        it, please?

Of all the books on the desk,       is of any use for our study.