Whose cake is the best.what grammatical name is given to this expression

If there were a question mark there instead of a period, I’d say it’s a question.

It's a question.

The expression "Whose cake is the best?" is an example of a comparative question. Comparative questions are used to ask about the superiority or preference of one thing over another. In this particular case, the question is seeking to know which cake is considered to be the best out of a group of cakes.

To answer the question and determine whose cake is the best, you would typically need to gather information by either tasting the cakes or getting opinions from others who have tried them. This way, you can compare the taste, appearance, texture, and other factors that contribute to the quality of a cake. Keep in mind that taste preference is subjective, so different people may have different opinions on which cake they consider to be the best.