In this English grammar error-spotting question, identify the part of the sentence that contains an error: "To the whale, its(A) tail is the sole(B) mean of propulsion.(C) No error(D)".

Introduction / Context:

Error-spotting questions check your ability to detect grammatical and usage mistakes in sentences. Here, the sentence talks about how a whale moves through water. You must identify which labelled segment, A, B, C, or D, contains the error, or choose "No error" if the sentence is correct. This type specifically focuses on correct use of singular and plural forms in standard English expressions.

Given Data / Assumptions:

- Full sentence: "To the whale, its(A) tail is the sole(B) mean of propulsion.(C) No error(D)".

- Part A: "its"

- Part B: "tail is the sole"

- Part C: "mean of propulsion"

- Part D: "No error"

- The sentence is intended to express that the whale uses only its tail in order to move or propel itself.

Concept / Approach:

The key idea here involves the expression "means of propulsion". In English, when we refer to an instrument, method, or way of doing something, we often use the plural form "means", even if it grammatically looks plural and is used for a single method. For example, we say "a means of transport", "by all means", and "a means of communication". The word "mean" without s is rarely used in this sense and would be incorrect in this fixed expression. Therefore, the error is in the use of "mean" instead of "means".

Step-by-Step Solution:

Verification / Alternative check:

We can reframe the sentence using standard expressions: "To the whale, its tail is the sole means of propulsion." This corrected sentence is fully idiomatic in English and clearly means that the tail is the only means by which the whale moves forward. A dictionary check for fixed expressions will confirm "means of propulsion" as normal usage. No other part of the sentence presents any grammatical or usage issues, so only Part C must be marked as the error.

Why Other Options Are Wrong:

Part A "its" correctly uses the possessive pronoun for "the whale". Writing "it's" here would be wrong, but that is not what appears. Part B "tail is the sole" is properly formed and matches subject-verb agreement. Part D "No error" would be correct only if no mistakes were present, but we have identified an error in Part C. Therefore, the only segment that needs correction is Part C.

Common Pitfalls:

Many learners are misled by the plural-looking form "means" and assume that when referring to one method, they must switch to "mean", which seems more singular. However, in standard English, the word "means" functions as both singular and plural in this context. The phrase "a means of" is therefore correct, not "a mean of". Being aware of such fixed expressions is essential for success in error-spotting questions, as they often test common idiomatic usage rather than purely mechanical grammar rules.

Final Answer:

The error is in part "C", where "mean of propulsion" should be corrected to "means of propulsion".