The organizers of the march issued a statement claiming that thousands of persons were present, but the police estimated the number to be nine hundreds. A. thousands of persons were present, but the police estimated the number to be nine hundreds. B. thousand of people to be present, but the police estimated the number to be nine hundred. C. thousands of people were present, but the police estimated the number to be nine hundreds. D. thousands of people were present, but the police estimated the number to be nine hundred. E. thousands of persons were present, but the police estimated the number to be nine hundred.

Subject-verb agreement is a fundamental aspect of GMAT grammar rules. It dictates that the subject and verb in a sentence must agree in number: singular subjects require singular verbs, and plural subjects require plural verbs.
For example:

• Correct: The cat runs quickly. (cat = singular, runs = singular verb)
• Incorrect: The cat run quickly. (cat = singular, run = plural verb)
• Correct: The cats run quickly. (cats = plural, run = plural verb)
• Incorrect: The cats runs quickly. (cats = plural, runs = singular verb)

Applying this rule helps us understand why consistent and accurate subject-verb agreement is essential for clarity and precision in writing.
In our exercise example, we focus on ensuring that the quantity terms ('thousands' and 'hundreds') match the numbers given. For instance, 'thousands of people were present' is correct because 'thousands' (plural subject) agrees with 'were' (plural verb). In contrast, 'nine hundred was present' would be incorrect because 'nine hundred' (plural subject) requires 'were' (plural verb). Paying close attention to this agreement helps construct grammatically correct sentences.

Understanding when to use plural and singular forms is essential for both GMAT grammar and effective communication. Singular forms refer to one item, while plural forms refer to more than one.
Consider these guidelines:

• Singular: Use when referring to one item. Example: a cat, an apple, one car.
• Plural: Use when referring to multiple items. Example: cats, apples, cars.

Special attention should be paid to irregular forms, such as 'person' (singular) and 'people' (plural). Incorrect usage like 'persons,' although grammatically acceptable, sounds awkward in modern English.
In our exercise, the correct answer identified that 'thousands of people' correctly signifies a large group (plural), while 'nine hundred' correctly represents a specific count of individuals (even though it's a large number, it's treated as a singular noun phrase). Therefore, avoid 'nine hundreds' because it incorrectly attempts to pluralize 'hundred' when a specific numerical count is already implied to be plural within context.

Making the right word choice in context is crucial for clarity and readability. Words must fit the context they are used in and align with common usage conventions.
In our exercise example, notice the difference between 'persons' and 'people':

• Persons: Often used in legal or formal contexts. It's grammatically correct but sounds outdated in everyday language.
• People: Common term for a group of individuals. Preferred in most scenarios for its familiarity and common usage.

The sentence provided in the exercise is more natural and comprehensible when using 'people' instead of 'persons.' Choosing the latter might make the sentence sound stiff or overly formal.
Additionally, correctly interpreting 'thousands' vs. 'thousands of people' can clarify large quantities intuitively for the reader. Proper word choice enhances meaning and engagement, ensuring the sentence structure is both grammatically accurate and contextually appropriate.