doloris wrote:

i do not understand.

can u please explain

Try plugging in numbers.

For A you must have numbers that are 5 apart. so lets use 10 and 5. we have 6,7,8,9. that is four numbers. now, since the question stem does not say that the numbers must be integers, try 10.5 and 5.5. now we have 6,7,8,9,10. thats five different integers.

this is not suff
For B, alone, this tells us nothing. It could be the number of integers between 675.463 and 345674, or it could be 1 and 1.1. This tells us nothing alone.

Now combine the two. Remember from part 1 when we tried the non-integers. So any numbers that are 5 apart, but are not integers will always have five integers between them.

Sufficient
answer is C