I vote A. I read the result/s initially as result per second.
Result(s) seems more natural, but I would prefer the option were you'd detect if the number is larger than 1 and change result to results.
Maybe take a look here: english.stackexchangeenglish.stackexchange here the (s) seems to be the standard.
Another option is to put it like this:
Matching results: 1
With this option the need to add/remove the 's' seems not as important as with your options.