Yes, it is B, it is a defining relative clause, notice that without the relative clause the sentence feels empty Only the players are going to get sunburned today.
Defining relative clauses use who/that for people, which/that for things and they are not delimited by commas.
Only the people that/who arrived first can enter.
This the house that/which I used to live in.
Non-defining clauses are just extra comments, optionally they can be removed about the previous noun/pronoun, they are separed by commas and that cannot be used.
Mary,who wears glasses, lives next door.
This country, which was a super power in the past, is still facing amajor economic crisis.