In the following question on error spotting, identify the part of the sentence that contains a grammatical error: As it was his first date, he dressed himself in best suit.

Introduction / Context:
Error spotting questions test a learner's command of grammar and idiomatic usage in English sentences. The given sentence talks about a man getting ready for his first date and asks which part contains an error. The key focus is on the noun phrase in best suit, where an important element is missing. Understanding the role of articles before nouns is essential to solve this question correctly.

Given Data / Assumptions:

• Complete sentence: As it was his first date, he dressed himself in best suit.
• Part A: As it was his first date,
• Part B: he dressed
• Part C: himself in best suit.
• Part D: No error.
• We assume standard modern English grammar rules.

Concept / Approach:
In English, singular countable nouns usually require an article or another determiner. The phrase in best suit sounds incomplete because suit is countable and singular. The correct expression is in his best suit, where the possessive determiner his specifies which suit is being referred to. The other parts of the sentence are structurally acceptable. Therefore, we need to identify the segment that lacks the necessary determiner.

Step-by-Step Solution:
Step 1: Examine part A: As it was his first date,. This part is a correctly formed subordinate clause indicating a reason or background. Step 2: Examine part B: he dressed. This is a correct simple past verb phrase functioning as the main clause predicate. Step 3: Examine part C: himself in best suit. Here, himself in is followed by the noun phrase best suit without a possessive or article. Step 4: Recall that the natural phrase in English is in his best suit, which includes the possessive determiner his. Step 5: Recognize that the error lies in part C because of the missing determiner. Step 6: Conclude that the answer must be C.

Verification / Alternative check:
Correcting the sentence confirms the analysis: As it was his first date, he dressed himself in his best suit. Now the sentence reads smoothly and naturally. There is no problem with the tense, verb agreement, or clause structure in parts A and B. Once part C is corrected with his, there is no remaining error, so the No error option in D is not correct. This confirms that the grammar problem is entirely within part C.

Why Other Options Are Wrong:
Part A is correct because As it was his first date is a properly formed dependent clause. Part B, he dressed, correctly uses the simple past tense with a third person singular subject. Part D, No error, is wrong because we have already identified a genuine error in part C. Hence, only part C contains the grammatical issue involving the missing determiner before best suit.

Common Pitfalls:
Learners may overlook the missing determiner because they are used to hearing shortened phrases in informal speech, such as in uniform or in hospital in some dialects. However, in examination English and formal writing, such omissions are generally not acceptable unless they follow specific idiomatic patterns. It is also easy to be distracted by other elements like himself and assume they are incorrect, although they are valid reflexive uses here. Careful reading of the noun phrase structure helps avoid such mistakes.

Final Answer:
The error is in part C, where himself in best suit should be himself in his best suit.