Respuesta :
Well a and b are eliminated instantly due to the fact of that you're trying to find the trait and in a and b you already have found it. So you have c and d and placing dogs in places to see if they get the trait can go wrong at any time due to the partner or certain genes. I would stick with c.
The answer is A because the question is asking for a particular trait and answer A says desired trait which is a synonym for particular trait.