Concept:This question tests the correct usage of the words "among" and "amongst" in a sentence.
Explanation:The three underlined parts are (a) "principal of the school", (b) "stressed the need for discipline", and (c) "amongst the students".
Part (a) correctly uses "principal" to mean the head of a school.
Part (b) correctly uses the verb phrase "stressed the need for discipline".
Part (c) uses "amongst", which is a valid alternative to "among" when referring to a group of people or things that are not distinct and are viewed as a collective.
Although "among" is more common in modern English, "amongst" is grammatically correct and often used in formal or literary contexts.
Thus, the sentence has no error in any underlined part.
Answer:(d) No error