range = largest number - smallest number
r>2????
b) z is smallest. no idea about largest. insufficient
a) w-z>2.
the largest number =w or >w, the smallest number=z or <z.. thus in any case, range >2
Sufficient.
IMO A

Statement 1
w-z>2. This implies that, if w where the largest number in the set and z the smallest, we satisfy the prompt. Now let's consider another case, in which w is not the largest, here w could be 5 and z could be 1 or 2. We also have two other integers. Clearly, either of x or y could be larger than w or either of x or y could be lower than z. In this case the Range would definitely be at least greater than 3. Sufficiency is achieved

Statement 2
z is the smallest number. We are not told that the other numbers are unique, so all the four numbers could be identical, in which case the range is 0 or the numbers could all be different and the range could be greater than 2. Insufficient

I made silly mistake and thought answer is C

u guys are right that by A range is atleast > 2...

Thanks