Data Sufficiency

Is the units digit of integer x2−y2 a zero?

(1) x−y is an integer divisible by 30

(2) x+y is an integer divisible by 70

(x+y)(x-y) --> INT-->doesnt means x & y are INT

Statement 1:
(x-y)/30
Suppose x-y = 60 --> x = 61.2 & y = 1.2
So, (x+y)(x-y) = 62.4 * 60 ==> _ _ 4 NO
Suppose x-y = 60 --> x = 61 & y = 1
so, (x+y)(x-y) = 62*60 ==> _ _ 0 YES
INSUFFICIENT

Statement 2:
(x+y)/70
Suppose x + y = 70 --> x = 71.2 & y = 1.2
So, (x+y)(x-y) = 72.4 * 70 ==> _ _ 4 NO
Suppose x + y = 70 --> x = 71 & y = 1
so, (x+y)(x-y) = 72*60 ==> _ _ 0 YES
INSUFFICIENT

Combining...
both (x-Y) & (x+y) has "0" as unit digit
SUFFICIENT

Answer [spoiler]{C}[/spoiler]

The way to question is written, in which x and y themselves could be decimals, the answer would be C. However, if x and y themselves have to be integers, then the answer would be A.