<em>Tania let her borrow the ipad, but she asked her to be careful </em>is a compound sentences because of the use of 'but'. Whenever you use <em>but, and </em>or <em>so</em> in a sentence, you are writing or stating a compound sentence since you are joining with such conjunction two independent clauses.
'a' is based on prediction. It's a future situation.The test will be next week and the students hope it will be easy
I think it might be search for the meaning of life.