Some of the question is missing, as are the answer choices.

if positive integer n is divisible by 5 and 7, then n must also be divisibile by which of the following.?

I. 12
II. 35
III. 70



a. none
b.I only
c. II only
d.I and II
e. II and III

Answer I is out of the question since n is a multiple of 35. However, why is choice III 70 wrong.
QA is C

The difference is between CAN BE and MUST BE...
n can be divisible by 70, whereas n must be divisible by 35

THANKS FOR THE INFO.. ITS THESE TYPES OF SUBTLE DIFFERENCES THAT GET ME.

simplyjat wrote:The difference is between CAN BE and MUST BE...
n can be divisible by 70, whereas n must be divisible by 35

Correct!

You always need to read the question carefully to determine exactly what it is that you're looking for.

If our number is a multiple of 5 and 7, we know it has to be a multiple of 5*7 as well (since they're both primes). Therefore, the minimum value of n is 35.

n could be any other multiple of 35, but since that's not what the question is asking, only II is a MUST be true: choose (c).