He goes there on . . . . . . . . horse back. A. a B. an C. the D. no article

The correct answer is: D. no article

The reason is that the word “horseback” is a compound noun, which means that it is made up of two words that are joined together to form a new word. In this case, the two words are “horse” and “back.” When a compound noun is made up of two common nouns, it does not take an article.

For example, we would not say “He goes there on a horse.” We would simply say “He goes there on horseback.”

Here are some other examples of compound nouns that do not take articles:

• headquarters
• breakfast
• toothbrush
• waterfall

Note that there are some exceptions to this rule. For example, if the first word of a compound noun is a proper noun, then the compound noun will take an article. For example, we would say “He goes there on the Eiffel Tower.”

Here are some other examples of compound nouns that take articles:

• the White House
• the United States
• the Great Wall of China

I hope this helps! Let me know if you have any other questions.