In the sentence "Sooner had he come his colleagues organised a get together", which underlined part contains the grammatical error that must be corrected?

Introduction / Context:
This error spotting question tests your understanding of a common correlative structure in English that uses no sooner with than. The sentence is broken into parts labelled A, B, C, and D, and you must decide which part contains the error. Carefully examining the standard pattern will help you identify what is missing or misused.

Given Data / Assumptions:

• The sentence fragments are: Sooner had he come (A) / his colleagues (B) / organised a get together (C) / No error (D).
• The intended meaning is that as soon as he came, his colleagues organised a get together.
• We assume the exam expects the standard formal pattern no sooner had he come than plus clause.

Concept / Approach:
The correct correlative expression is no sooner plus auxiliary verb plus subject plus past participle, followed by than and another clause. For example, No sooner had he come than his colleagues organised a get together. In the given sentence, the word no is missing before sooner, and there is no than connecting the two clauses. The main detectable error in the broken parts is in part A, which begins with Sooner had he come instead of No sooner had he come.

Step-by-Step Solution:
Step 1: Recall the full idiomatic structure: No sooner had he arrived than they welcomed him.Step 2: Compare this pattern with the given first part Sooner had he come.Step 3: Notice that the word no is missing, so the phrase no sooner is incomplete in part A.Step 4: Recognise that parts B and C, his colleagues and organised a get together, form a normal subject verb object group and are otherwise acceptable.Step 5: Conclude that the primary and testable error lies in part A, which should read No sooner had he come rather than Sooner had he come.

Verification / Alternative check:
Rewrite the sentence correctly as a whole: No sooner had he come than his colleagues organised a get together. Now break it into parts again. The phrase No sooner had he come is complete and idiomatic. The second clause his colleagues organised a get together is also correct. Since the question is about identifying the part with the error, and the only missing crucial word appears at the start, part A must be chosen.

Why Other Options Are Wrong:
Part B, his colleagues, correctly supplies the subject of the second clause, so it has no grammatical fault. Part C, organised a get together, uses the past tense verb organised plus object and is acceptable in standard English. Part D, No error, is wrong because we have clearly found an error in the form of the incomplete expression Sooner had he come, which lacks the important word no.

Common Pitfalls:
Students sometimes focus too narrowly on verb forms and miss correlative pairs like no sooner and than or hardly and when. Exam setters often exploit this by removing only one small word. A good strategy is to train yourself to recognise these fixed pairs so that you can immediately see when a sentence like Sooner had he come is missing no sooner plus than. Marking the first part as containing the error then becomes straightforward.

Final Answer:
The grammatical error is in the first part, which should read No sooner had he come, so the correct choice is A, and option A is correct.