The correct answer is Option B.
WHO'S is the contraction of WHO IS.
In the given sentence the speaker is asking about the person who will win Wimbeldon this year.
Thus WHO IS the correct answer as WHO is used to ask about a person. WHOSE is a possessive pronoun used to ask about belonging.
In the given sentence there is no mention about someone's belonging.
Thus WHOSE is incorrect and WHO'S is the correct answer.
The remaining options are incorrect because:
Option A- NO CHANGE is incorrect because WHO'S is the correct answer.
Option C- WHICH IS used when one has to choose from a variety of options.
Option D- WHAT IS is used to ask about some information.