Which of the following sentences demonstrates correct grammar?

It contains all three components of a sentence which is noun, subject and the object.

The correct usage is "fewer" when referring to countable items like people. Therefore, the grammatically correct sentence is:

b. If any fewer people watch that television series, the effect will be its cancellation.

It clearly explains the paragraph as there are physical and psychological reasons for a daily walk.

Adverb, it explains more about the verb

Datum - singular form of data

Parenthesis - singular form of parentheses

Thesis - singular form of theses

Syllabi - plural form of syllabus

Choice B is correct, as explained below.
"I plan to enroll in College next year" incorrectly capitalizes the word "College." The general rule for capitalization is that common nouns, such as "college," should not be capitalized unless they are part of a proper noun or a specific institution's name.

Corrected, the sentence would be: "I plan to enroll in college next year." Kindly note that the question asks for the incorrectly capitalized sentence.

The other choices are wrong as below:

Choice A: The Geography students took a class trip to the Rocky Mountains.

• This sentence correctly capitalizes "Geography" because it is the name of a specific subject or course. "Rocky Mountains" is also capitalized because it refers to a proper noun (a specific mountain range).

Choice C: Even though he moved to New York, he was born in a Western town.

• "New York" is correctly capitalized as it is the name of a specific state. "Western" is capitalized because it is part of the proper noun "Western town" which refers to a specific town in the Western region.

Choice D: The A1 Plumbing Board of Directors gave every employee a raise.

• "A1 Plumbing Board of Directors" is a specific organization's name, so all parts of it are capitalized appropriately.