The correct answer is D. No error.
The sentence is grammatically correct. The word “as” is used to introduce a reason, and the phrase “they interfere in serious study”
is a reason why students should not take part in party politics and political demonstrations.The other options are incorrect because they contain grammatical errors. Option A is incorrect because the word “should” should be followed by an infinitive verb, not a participle. Option B is incorrect because the word “in” is not necessary after the preposition “party.” Option C is incorrect because the word “as” is not necessary after the conjunction “and.”