Can you please check these sentences for me, please? Thank you very much.

1) There are other teenagers who like wearing baggy jeans.
You'll listen to the test twice.
2) You are asked either to cross the correct alternative (among three) or to fill in the blanks with a suitable word. Remember not to write anything in pencil otherwise your test won't be evaluated.
3) Put away everything you have on your desk. You are not allowed to use dictionaries or photocopies.
4) You mustn't keep your cell phone on the desk
5) If you are absent during your afternoon revision test, your parents will have to justify your absence in your excuse card (slip?)

1. OK

2. Second sentence here is a run-on. How will you fix it?
http://grammar.ccc.commnet.edu/grammar/runons.htm

3. OK

4. OK

5. ... on your excuse card.