C. the - We use "the" when referring to a specific part of the world (the world).

B. the / the - "The book I lent you" refers to a specific book. "Last week" specifies a particular week.

B. X / the - We don't use an article before "train" when referring to traveling by train in general. "The West of England" is a specific region.

D. the - "The United States" is a proper noun that requires "the."

C. X - We don't use an article before abstract nouns like "love" when used in a general sense.

A. The / X - "The schooling" refers to the system of schooling in general. We don't use an article before "ages" in this context.

A. X / X - We don't use articles before "most social situations" when referring to them generally, nor before "informality" as it's an abstract noun used generally.

B. The / X - "The love" refers to love as a concept. We don't use an article before "very strong feeling" because it's a general description.

D. the capital - London is the capital of England (a specific capital).

C. the - "The number" refers to a specific number.

D. X - We don't use an article before "wild" when referring to animals in the wild in general.

B. A / a - This is a proverb: "A friend in need is a friend indeed."

C. the / X - "The biggest dream" refers to a specific dream. We don't use an article before "life" when referring to life in general.

A. a - "A good time" is a common expression.

A. a / the - "A campaign" refers to one specific campaign. "The disabled" refers to a specific group of people.

C. The - "The most important thing" refers to a specific thing.

D. X - We don't use an article before sports like "football" when referring to them generally.

C. the - "The Nile River" is a proper noun that requires "the."