A, because all the other are in direct reference to something
The third answer is your best choice.
Answer:
1. I think it means that many people are studying their whole lives that they forget other important things.
2. That's the quoter's last name
3. You know less about other things, like social skills, or how to cook.
4. (Dunno, sorry)
5. (This applies to you)
Explanation:
No comment
A Simple Sentence, is simply a sentence that consists of only one clause, with only a single subject and predicate.
Example: (in picture below)
~Hope this helped :)