Fill in the blank choosing the suitable article from the options below.
I take ___ hour to reach my office.

Correct option is A

The correct option is (a) an.

Explanation:
The rule for using the indefinite article an is based on the sound of the first letter of the following word, not its spelling. The word hour begins with the letter h, but the h is silent — it is pronounced /aʊər/, which starts with a vowel sound. Therefore, the article an must be used before hour.

Grammatical Rule (English):

• Use a before words that begin with a consonant sound.
• Use an before words that begin with a vowel sound (regardless of the spelling).
• Examples: an hour, an honest man, an heir (all have silent h).

• (b) the – The definite article; used for specific or previously mentioned nouns. Not appropriate here as no specific hour is being referred to.
• (c) no article – An article is required before a singular countable noun like hour.
• (d) a – Used before consonant sounds; hour begins with a vowel sound, so a is incorrect.