Four sentences are given below as A, B, C and D. Choose the sentence that is grammatically incorrect in describing crowds of commuters at railway stations.

Introduction / Context:
This question checks your command of natural English expression when describing very large crowds, a common theme in reading comprehension and sentence improvement tasks. The focus is on how to express the idea that huge numbers of commuters, comparable to the population of a small nation, pass through railway stations every day.

Given Data / Assumptions:
Four alternative sentences describe crowds at railway stations.
All refer to people commuting from faraway or distant places.
Each sentence tries to compare the size of the crowd to that of a small nation.
You must find the sentence that is grammatically or stylistically unacceptable in standard English.
Assume formal written style suitable for essays, reports, or examinations.

Concept / Approach:
The approach is to evaluate each option for grammar, word order, and natural collocations. English allows various ways to express numerical comparisons, such as in numbers comparable to those of a small nation or as many people as in a small nation. Expressions like numerical magnitude of small nations are extremely awkward and not used in idiomatic English. We also look at whether the use of passive verbs like are poured out is acceptable or unnecessarily clumsy.

Step-by-Step Solution:
Step 1: Read option A. The structure as many people as those in a small nation can be seen at stations is somewhat wordy but grammatically acceptable and clearly expresses the comparison. Step 2: Read option B. Railway stations pour out commuters from faraway places every day in numbers comparable to those of a small nation uses pour out metaphorically and forms a clear and correct sentence. Step 3: Read option D. Every day, stations are crowded with commuters from distant places in numbers comparable to those of a small nation is also well formed and natural. Step 4: Read option C. People of a numerical magnitude of small nations commuting from faraway places are poured out by the stations every day is clumsy and ungrammatical. The phrase people of a numerical magnitude of small nations is not standard, and the passive are poured out by the stations sounds very unnatural. Step 5: Conclude that only option C clearly violates natural English usage and is therefore the incorrect sentence.

Verification / Alternative check:
You can try simplifying each sentence to test its structure. In option C, if you reduce the modifiers, you get people of a numerical magnitude of small nations are poured out by the stations, which still sounds unnatural. In contrast, simplified versions of the other options, such as stations pour out commuters every day in huge numbers, remain clear and idiomatic. This confirms that option C is the odd one out.

Why Other Options Are Wrong:
Option A is acceptable because as many people as those in a small nation is a valid pattern of comparison, even if a little heavy.
Option B is acceptable because pour out commuters is a common metaphor and the comparison in numbers comparable to those of a small nation is correct.
Option D is acceptable because are crowded with commuters and in numbers comparable to those of a small nation are both grammatically sound phrases.
Only option C uses an unidiomatic and confusing phrase numerical magnitude of small nations, so it is the incorrect one.

Common Pitfalls:
Learners often focus only on subject verb agreement and overlook awkward noun phrases. Even though every verb appears to agree in number in option C, the overall phrase is not natural English. Another pitfall is assuming that all complex or long sentences are automatically correct in formal writing, but examinations often reward clarity and natural collocations over unnecessary complexity.

Final Answer:
The grammatically incorrect sentence is Option C. People of a numerical magnitude of small nations commuting from faraway places are poured out by the stations every day.