Identify the part of the sentence that contains an error in The boy who (1) sat close him (2) was his son. (3).

Introduction / Context:
This error spotting question checks your understanding of correct prepositional phrases in English. The sentence is divided into numbered segments: The boy who, sat close him, was his son, and No Error. You need to identify which segment contains incorrect or incomplete grammar. Such questions are common in exams because they focus attention on small but important details like prepositions and relative clauses that can easily be overlooked in normal reading.

Given Data / Assumptions:

The full sentence is The boy who sat close him was his son.

Part 1 is The boy who.

Part 2 is sat close him.

Part 3 is was his son.

Part 4 represents No Error.

We want a natural English sentence that states which boy was his son.

Concept / Approach:
The main structure is a relative clause describing the boy. The phrase sat close him is incorrect because the preposition to is missing. In English, we say sit close to someone, stand next to someone, or sit near someone. The correct form here is sat close to him. The rest of the sentence, The boy who and was his son, is grammatically correct when combined with the corrected middle part. Therefore, the error exists in segment 2, which omits the required preposition to after close.

Step-by-Step Solution:
Step 1: Read the sentence silently as if it were one piece: The boy who sat close him was his son. Step 2: Focus on the phrase sat close him and ask whether this matches natural English usage. Step 3: Recall that the usual expression is sit close to a person or sit close by someone, not sit close someone. Step 4: Replace sat close him with sat close to him and see that the full sentence now becomes The boy who sat close to him was his son, which is correct. Step 5: Confirm that parts 1 and 3, The boy who and was his son, work perfectly with the corrected middle part, so only part 2 contains an error.

Verification / Alternative check:
Compare this sentence with similar correct sentences. For example, The girl who sat next to me was my friend uses next to with a preposition. Another example is The child who sat close to her mother felt safe. In both cases, a prepositional phrase close to or next to a pronoun or noun is required. Without to, the phrase becomes ungrammatical. If we try to construct other sentences with close followed directly by a pronoun, they sound wrong. This shows that the error is indeed the missing preposition to in segment 2.

Why Other Options Are Wrong:
Option A The boy who correctly introduces a defining relative clause and has no grammatical problem. Option C was his son forms the main verb phrase of the sentence and is correctly constructed in simple past tense. Option D No Error would only be correct if all three segments were grammatically sound, but the missing preposition in part 2 proves that this is not the case.

Common Pitfalls:
Learners sometimes overlook small missing words like prepositions because meaning is still understandable from context. Another pitfall is thinking that close can be used like near without a preposition. In fact, we can say he stood near him but usually say he sat close to him. Remember that close to is a standard collocation when referring to physical proximity between people or objects. Training yourself to pay attention to these small patterns will help you catch similar errors quickly in examination questions.

Final Answer:
2