People attracted onto Facebook with the promise of fun, free service don’t realize they’re paying for it by________ their personal information. 

—Peter, this is Laura, a student from No. 2 Middle School.—How do you do? I’m very delighted to make your _______.

(2013·天津，2)If you are in trouble，Mike is always willing to________a hand.

We have to admit that the biggest___________ facing the ecosystem is limited resources and the worsening environment.

If you live in the country or have ever visited there, ______ are that you have heard birds singing to welcome the new day.