A. Whoever would pitch in the game had a tough battle against the best hitters in the league.
Explanation:
Noun clause includes the phrase containing the noun and functioning as either the subject or as the predicate of the sentence. These clauses are a fragment that is dependent on the principal clause. Among the given options, option A illustrates the noun clause "whoever would pitch in the game" that is functioning as the subject as well as verb. Thus, option A is the answer.
