Data Sufficiency

IMO: A

If z is a positive integer, is Z+1 is a factor of 105?

1. Z is a factor of 20.

Z can be 1,2,4,5,10,20
Z+1 can be 2,3,5,6,11,21. Of which only 21,5,3 are factors of 105 and the rest aren't.
So, statement 1 is insufficient to answer the question.

2. 10 is a factor of z.

Z can be 10,20,30,....
Z+1 can be 11,21,31...
If Z+1 is 11, it is not a factor of 105.
If Z+1 is 21, it is a factor of 105.
So, statement 2 is insufficient to answer the question.

From 1 + 2

Z can be 10 or 20.
If Z = 10, Z+1 = 11 is not a factor of 105.
If Z = 20, Z+1 = 21 is a factor of 105.
So, statement 1+2 combined is insufficient to answer the question.
IMO E