3 part preflop quiz

[Marquis]

Here's the situation (9-handed):

Preflop: Hero is UTG+1 with two cards.
UTG calls, Hero calls, MP1 calls, <font color="#CC3333">MP2 raises</font>, <font color="#666666">2 folds</font>, Button calls, SB folds, <font color="#CC3333">BB 3-bets</font>, UTG calls, Hero ?

Assume opponents with reasonable raising and 3-betting standards. Original raiser will only cap with AA, KK and AKs. What do you do if you hold:

a) QJs?
b) A5s?
c) 55?