Topic: Article,

Best Answer Explained in Below-:

The sentence "Many __ good boy failed." requires the correct article to precede the noun phrase "good boy." To understand why "C) a" is the correct choice, we need to analyze the grammatical rules governing the use of articles in English.

1. **Indefinite Article "a"**: The article "a" is used before singular, countable nouns that begin with a consonant sound. In this case, "good boy" is a singular noun that is also countable, making "a good boy" appropriate. The phrase "many a" is a common construction that introduces the phrase in a formal or literary context, indicating that there are numerous instances of singular boys who are good.

2. **"The"**: Option A, "the," is a definite article that refers to a specific noun. In this case, "the good boy" would imply that there is one specific good boy being discussed, which contradicts the plural "many."

3. **"An"**: Option B is an indefinite article used before nouns that begin with a vowel sound. "Good" does not begin with a vowel sound, making "an" inappropriate in this context.

4. **"None"**: Option D indicates the absence of an article, which fails to meet the grammatical requirements of the sentence.

Thus, the correct article is "a," resulting in the phrase "Many a good boy failed," effectively conveying that numerous singular boys exemplified the characteristic of being good but ultimately failed.