Error spotting in noun number: One of the assistant was Alfred. Identify which part of this English sentence is grammatically wrong or state that there is no error.

Introduction / Context:
This question tests correct noun number after the phrase one of. The sentence refers to Alfred as one member of a group of assistants. English grammar requires a plural noun after one of to show that the individual is part of a larger group. Competitive exam questions often include this pattern because it is a frequent area of error for learners.

Given Data / Assumptions:
- Sentence: One of the assistant was Alfred.
- Part (a): One of the assistant
- Part (b): was
- Part (c): Alfred
- Part (d): No error
We assume that the meaning is that Alfred belonged to the group of assistants.

Concept / Approach:
The structure one of is always followed by a plural noun, for example one of the students, one of the books, one of the teachers. The verb usually agrees with one, so it is singular. Therefore, the correct phrase here should be one of the assistants, not one of the assistant. The verb was and the proper noun Alfred are both correct, so the mistake is confined to the first part of the sentence.

Step-by-Step Solution:
Step 1: Examine part (a) One of the assistant. Here, assistant appears in the singular form following the phrase one of. Step 2: Recall the rule: after one of, the noun must be plural because you are choosing a single item out of a larger group. Step 3: Therefore, the correct expression should be one of the assistants. Step 4: Check part (b) was. Since one is grammatically singular, the verb was is the correct past tense form of be. Step 5: Check part (c) Alfred. This is simply a proper noun identifying which assistant is meant, and it is correct. Step 6: Since parts (b) and (c) are correct, only part (a) contains an error.

Verification / Alternative check:
We can rewrite the corrected sentence as: One of the assistants was Alfred. This version now follows the standard pattern: one of plus plural noun plus singular verb plus complement. Another check is to imagine a similar sentence such as One of the cars was stolen, which clearly uses a plural noun after one of. This comparison confirms the correction.

Why Other Options Are Wrong:
- Error in part (b) only: Was is the correct singular verb for the subject one, so this is not an error.

- Error in part (c) only: Alfred as a proper noun is correctly placed and capitalised, so part (c) is correct.
- No error in the sentence: Accepting this would allow a singular noun after one of, which is not standard, so this option is wrong.
- Error in more than one part: Only the noun in part (a) needs to be changed, so multiple errors is not a correct judgment.

Common Pitfalls:
Many learners focus only on the nearest noun and may think that assistant looks reasonable after the article the. They forget the special rule that one of must be followed by a plural noun because it indicates selection from a set. Paying attention to fixed patterns like one of the plus plural noun can help avoid such errors in exam situations.

Final Answer:
Correct option: Error in part (a) only.