In the following sentence, one part may contain an error. Identify the part with the error; if there is no error, select "No Error": No sooner did I come out of my home to go to market (1) / when it started raining heavily (2) / which drenched me completely. (3) / No Error (4).

Introduction / Context:
Error spotting questions train candidates to detect common grammatical mistakes in English sentences. They often focus on fixed expressions, conjunctions, and word pairs that must be used together. In this sentence, the structure begins with No sooner, which belongs to a well known correlative pair in English grammar. Recognising the correct partner word for No sooner is the key to solving the question.

Given Data / Assumptions:
The sentence given is: No sooner did I come out of my home to go to market (1) / when it started raining heavily (2) / which drenched me completely. (3) / No Error (4). We are told that exactly one part may contain an error. The focus is on the combination No sooner did, followed by another clause introduced by a conjunction. We assume standard formal English usage as expected in competitive examinations.

Concept / Approach:
The correlative conjunction pattern with No sooner in English requires the pairing No sooner... than..., not No sooner... when.... The structure is: No sooner did or had subject verb, than subject verb. Therefore, after the first clause No sooner did I come out of my home to go to market, the second clause must begin with than, not when. This is a fixed pattern tested frequently, and using when here counts as a grammatical error.

Step-by-Step Solution:
Step 1: Identify the expression No sooner at the beginning of the sentence.
Step 2: Recall that the correct correlative pair is No sooner... than.
Step 3: Observe the first clause: did I come out of my home to go to market, which is correctly formed with inversion.
Step 4: Notice that the second clause in part 2 starts with when, which does not match the required pattern.
Step 5: Conclude that part 2 contains the error and that when should be replaced by than.

Verification / Alternative check:
Rewrite the sentence with the correction: No sooner did I come out of my home to go to market than it started raining heavily, which drenched me completely. This version sounds natural and follows established grammatical rules. If we keep when instead of than, the sentence sounds awkward and incorrect in formal written English. This comparison confirms that the error lies in part 2 and that the correct conjunction should be than.

Why Other Options Are Wrong:
Part 1 correctly uses the auxiliary did with inversion after No sooner, matching standard usage. Part 3, which drenched me completely, is a proper relative clause describing the effect of the heavy rain. Part 4 is only the label No Error for the entire sentence and is not itself erroneous. Therefore, only part 2 contains a genuine grammatical problem, making option B the correct choice.

Common Pitfalls:
Students often confuse structures like No sooner... than, Hardly or scarcely... when, and Barely... when. Each of these fixed pairs has a particular partner conjunction. Mixing them leads to errors such as No sooner... when or Hardly... than. A practical method is to memorise small pattern cards: No sooner... than, Hardly or Scarcely... when or before. When answering exam questions, quickly check whether the correct pair has been used.

Final Answer:
The error is in part 2; the conjunction when should be replaced by than to complete the correct pattern No sooner... than.