The correct option is A plenty of
We use ‘plenty of’ before an uncountable noun with negative and affirmative sentences. Here, the sentence states a fact about the Kohinoor diamond, making the sentence an affirmative sentence. It also uses the quantifier ‘plenty of’ before the uncountable noun ‘fame’. ‘Much’ is only in negative and interrogative sentences. Therefore, ‘plenty of’ is the correct answer.