In the following sentence error question, identify the part which contains a grammatical error, if any: “On being called, / all of us / entered into the room. / No Error”.

Introduction / Context:
Error spotting questions test a learner's command of English grammar and usage. In this sentence, the structure is divided into four parts, and we must find which part contains a mistake. The focus here is on correct use of the verb “enter” with respect to prepositions, a common area of confusion in English exams.

Given Data / Assumptions:

• The full sentence is: “On being called, (A) / all of us (B) / entered into the room. (C) / No Error (D)”.
• We must choose the part A, B, C, or D where the error lies.
• If there is no error, we would choose D.

Concept / Approach:
The key grammar rule involved here concerns the verb “enter”. In standard English, “enter” is a transitive verb, which means it usually takes a direct object without a preposition when indicating movement into a place. We say “enter the room”, not “enter into the room”. The phrase “enter into” is used in different senses, such as “enter into an agreement” or “enter into a discussion”, where the meaning is more abstract. In the physical sense of going inside a room, “into” is unnecessary and incorrect.

Step-by-Step Solution:
Step 1: Examine Part A: “On being called,”. This introductory phrase is correct and serves as an adverbial clause of time. Step 2: Examine Part B: “all of us”. This is a correct subject phrase referring to the group. Step 3: Examine Part C: “entered into the room.” This is where we must check the verb and preposition usage. Step 4: Apply the rule for “enter”. The correct expression for physical movement is “entered the room”, without “into”. Step 5: Conclude that Part C contains the error. The correct sentence should read: “On being called, all of us entered the room.”

Verification / Alternative check:
To verify, we can test the sentence against other examples: “She entered the hall”, “The students entered the classroom”, “They entered the building”. In each case, no preposition is used after “entered” when referring to a place. This pattern confirms that adding “into” in this context is non standard and considered incorrect in formal English grammar questions.

Why Other Options Are Wrong:
Option A: “On being called,” is a standard non finite clause and grammatically fine. Option B: “all of us” correctly functions as the subject and has no error. Option D: “No Error” cannot be correct because we have already identified a clear usage mistake in Part C.

Common Pitfalls:
Because many people use “enter into” in everyday speech, students sometimes think it is acceptable in all contexts. Another confusion arises because other verbs like “go into” and “come into” are correct, so learners wrongly apply the same pattern to “enter”. For exam purposes, always remember that “enter” directly takes an object when indicating physical movement to a place, and avoid adding “into” in such cases.

Final Answer:
The error lies in Part C, where “entered into the room” should be “entered the room”. Therefore, the correct answer is C.