A 33  half-watt resistor and a 330  half-watt resistor are connected across a 12 V source. Which one(s) will overheat?

ANS:D - neither resistor

The word across means parrallel,

ie. The two resistance are parallel to the voltage (12v) source,

Then, both resistance have 12 volts resistance across then,

Then the power source across 33ohm is using v^2/R = 12^2/33 = 4.36 watts (overheat) ,

With 330 ohm, power = 12*12/330 =0.436 watts (won't over heart).

Therefore, the answer is "A".