science
posted by Ros .
What would a counterexample be in math?
a.an example that proves the conjecture wrong
b.an example to show the formula is wrong
c.a very nice granite kitchentop surface
d.an example to show the conjecture is true

Since this is not my area of expertise, I searched Google under the key words "math counterexample" to get this:
http://www.google.com/search?client=safari&rls=en&q=math+counterexample&ie=UTF8&oe=UTF8
In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search. Also see http://hanlib.sou.edu/searchtools/.