D. a nuclear power plant.
The answer to the first question is
4. a present-tense verb in a dependent clause.
The answer to the second question is
2. The words are an infinitive phrase that functions as an adverb modifying the verb comes.
The answer is:
Extra-curricular activities can help students learn more about subjects they’re interested in.
This portrays extra-curricular activities in a positive way. The rest make extra-curricular activities seem like a burden.