The correct answer is alternative A.
Positive thinkers are able to think in different contexts, and this leads to more creative solutions. Once you focus on the positive side of things your mind starts seeing the good sides on each and every thing, even the bad ones, and by seeing things this way the brain comes up with more alternatives to solve problems.
Having negative thinking leads to less alternatives to solve problems because your brain gets blinded and it doesn't see the solutions and possibilities so clearly.