drying agents

[hana]

Q) Which of the following pairs of gases can be dried using conc.H2SO4 as well as anhydrous CaCl2?
1. NH3 and SO2 2. SO2 and F2 3. Cl2 and HCl 4. Cl2 and F2 5. HCl & SO2

Here's what I think,
Inorder to succesfully act as drying agents,both conc sulphuric and CaCl2 should not react with the chemicals provided,right?
So... in,
1. NH3 would react with sulphuric to give ammonium sulphate(I think),so one's out.
(I would really appreciate it ,if someone could check my other reactions,too,
SO2 + H2SO4 would not react
CaCl2 + SO2,I'd like to think they don't react)

2. I think (only) fluorine would react with CaC2 to give CaF2 and Cl2,
so we're left with 3,4 & 5

3. Nothing reacts ?

4. (only?) F2 would react with CaCl2 to give Cl2 gas and CaF2

5. no reactions?,
So I'm left with 2 choices(3 and 5)?
but there can't be 2 answers?
I'm hoping someone could help me with the reactions and help me determine the answer.
Inorganic chemistry is my worst subject so ,I would really appreciate a detailed explanation of the reactions taking place (if at all),and why

Thank you