Answer: c. the products would no longer be similar in the wheat market.
Explanation;
In a perfectly competitive market, goods are meant to be homogeneous which leads to stiffer competition as a consumer could just switch from one seller to another and still get the same utility as all products are similar.
If one product starts to taste better and have fewer calories, the products in the market will no longer be homogeneous and competition will decrease because switching to this newer wheat would increase a consumer's utility as opposed to not therefore more people will switch and other competitors will not be able to compete unless they start producing better wheat as well.