This is ___ unique opportunity. Choose the correct article:

Answer: option D ‘a’

Explanation:

The word "unique" begins with a 'y' sound (pronounced as 'yoo-neek'), which is a consonant sound. Therefore, the indefinite article "a" is used instead of "an." The use of articles in English depends on the sound that follows them, not just the letter. "An" is used before vowel sounds, while "a" is used before consonant sounds. In this case, even though "unique" starts with a vowel letter 'u', it is the sound that follows the article that determines its form, and "unique" starts with a consonant sound.