Error spotting in comparative sentence: identify the part with an error in "The population of Mumbai is greater than in any city in USA"

Introduction / Context:
This grammar question tests error spotting in a comparative sentence that contrasts the population of Mumbai with that of cities in the United States of America. The challenge lies in correctly comparing quantities and using appropriate prepositions and structures. Such questions are common in competitive exams to check whether candidates can maintain grammatical parallelism in comparisons.

Given Data / Assumptions:

• The sentence is divided into four parts for error identification.
• Part A: "The population of Mumbai"
• Part B: "is greater than"
• Part C: "in any city in USA."
• Part D: "No error"
• The intended meaning is that the population of Mumbai is greater than the population of any city in the USA.

Concept / Approach:
When comparing quantities like populations, we must compare like with like. The phrase "the population of Mumbai" should be compared with "the population of any city in the USA", not with "in any city in USA". The word "in" makes the phrase ungrammatical because it introduces a prepositional phrase instead of a noun phrase that matches "population". Correct usage would be "that of any city in the USA" or simply "the population of any city in the USA".

Step-by-Step Solution:
Step 1: Read the sentence as a whole: "The population of Mumbai is greater than in any city in USA." Step 2: Notice that the comparison is incomplete: we do not have a clear noun phrase after "than" that corresponds to "population". Step 3: Recognise that the correct comparison should be between two populations, so we expect something like "than that of any city in the USA". Step 4: Identify where the problem starts. The phrase "in any city in USA" begins in part C. Step 5: Realise that "in any city in USA" is not parallel to "the population of Mumbai" and therefore introduces the error.

Verification / Alternative check:
Construct a corrected version of the sentence: "The population of Mumbai is greater than that of any city in the USA." Here, "that" refers to "population", so both sides of the comparison match. We could also say, "The population of Mumbai is greater than the population of any city in the USA." In both cases, the error is removed by replacing the problematic phrase from part C. Parts A and B remain unchanged, which confirms that the error lies specifically in part C.

Why Other Options Are Wrong:
Option A (Part A): "The population of Mumbai" is grammatically correct and clearly introduces the subject of comparison. Option B (Part B): "is greater than" is the correct comparative phrase to express that one quantity is larger than another. Option D (No error): This would only be correct if no part of the sentence contained a grammatical problem. Since part C is faulty, option D cannot be chosen.

Common Pitfalls:
A frequent mistake is to ignore the need for parallel structure in comparisons and to accept "than in any city" because it sounds somewhat natural in quick speech. However, in formal written English, especially in exam contexts, comparisons must be precise. Another pitfall is to think there is an error in article usage with "the USA". While it would be preferable to add "the" before USA, the main tested error here is the comparative structure in part C.

Final Answer:
The error is in part C, so option C is the correct choice.