The correct option is D than
An adverbial clause is a group of words that modifies an adjective, verb or adverb. Here, the subordinate clause (Pedro does) is the adverbial clause that modifies the verb 'plays'. In such sentences, the verb is not mentioned in the subordinate statement. A subordinate clause is a clause that depends on the main clause (Lenny plays far more complex music) for its full meaning. Since the given sentence is of the comparison degree, the adverbial clause of comparison, using the conjunction 'than' is used, making "than Pedro does" the adverbial clause of degree of comparison. Hence 'after' is not used here, and 'than' is the appropriate option. So option A is incorrect and D is correct. 'If' is a conjunction used when the subordinate clause is a condition. a situation that decides the action in the main clause, example, "I will join the party if Susan accompanies me". Since the clause here is not conditional, 'if' will not be used, option B is incorrect. 'Because' is a conjunction used when the subordinate clause is the cause for which the main clause is the effect, example, "Lenny plays well because he's been practicing since childhood". As the given subordinate clause is not a cause, option C is incorrect.