I will go with A on this..
we know that a cube has 3 sides colored red...then we dont care what the others are...3/6 or 1/2 of the surface area is red...we dont care about the other surface..we just know that exactly 3 are red..thats sufficient..
What fractional part of the total surface area of cube C is red?
(1) Each of 3 faces of C is exactly red.
(2) Each of 3 faces of C is entirely white.
I thought answering this as nobody has addressed this question.
Statement1 says each of three faces is exactly red. It does not say anything about other three faces. So you don't know about other three faces they can be red or not. So insuff.
Same with statement 2, we are not sure which three faces he is talking about. so Insuff.
Combining them together- now we know that three faces are red and three faces are white. hence gives the fraction of surface area which is red.
ANSWER IS 'C' --this is more of a english twister rather than a PS question