I go with C.

I go with C too, but why?

Because with stmt 1 alone is not sufficient and stmt 2 alone would be sufficient if it is mentioned that 'S' is positive but since this is not stated explicitly 'S' and be -ve and if its -ve 0 wont lie between r and s.

Now since stmt 1 says 'S' is positive we can derive the result from stmt 2.

So, both stmts together are sufficient.

Correct me if I am wrong.

Yes combining both will information that

-s and r are same point on the number line so C.

C
Here is my approach

The problem can be rewritten as

Is s = -r ?

Stmt 1 is not sufficient.

Stmt 2 can be written as t -r = t - (-s) OR r -t = t -(-s)
simplifying s = -r. OR r -t = t + s.

Using both stmts, we get s = -r. So C