Hi please consider this:
Set A {1,2,3,4,5,6,7,8,9,10} from which two sets have to be created which contain distinct integers only. To find integers used twice, we have to look for overlaps in set p and set q
Statement 1: Set P has 8 elements whereas Set Q has 7
Set P can be {1,2,3,4,5,6,7,8} and Set Q can be {1,2,3,4,5,6,7}- overlap of 7 integers
Set P can also be {1,2,3,4,5,6,7,8} and Set Q {10,9,8,7,6,5,4} - overlap of 5 integers
Since it is given that each integer from Set A has to be used at least once hence we take the second case
Statement 1 is sufficient
Statement 2:
Sum of P+Q - Sum of A=15
15 can be the sum of 5 distinct integers at max ie. 1,2,3,4,5 but since we are not given how many elements to choose the elements may well be 4,5,6
Statement 2 is not Sufficient
In case the "must be used once" condition was absent in Set A, then Statement 1 would have gotten interesting.
Max overlap is 7 and Minimum overlap is 5 between two 7 and 8 element sets. Then Statement 1 would be insufficient and you would have to use the fact that sum of 15 can be achieved by a maximum of 5 distinct positive integers {1,2,3,4,5,}
Hence then the Answer would have been C
Here of course the Answer is A