The correct answer is C. plentiful.
The word “copiously” means “in large quantities or amounts.” In this sentence, the speaker is drawing examples from a variety of books. This means that they are using a lot of examples, or a plentiful amount of examples.
The other options are not as accurate. The word “largely” means “to a great extent or degree.” In this sentence, the speaker is not necessarily using a great extent or degree of examples. The word “continuously” means “without interruption.” In this sentence, the speaker is not necessarily using examples without interruption. The word “completely” means “in every way or respect.” In this sentence, the speaker is not necessarily using examples in every way or respect.
Therefore, the correct answer is C. plentiful.