Fill in the blank with the correct article.
______ book you were looking for has now come out in Kindle edition.

Correct option is A

The correct answer is (a) The.
The sentence refers to a specific book already known to the listener/reader—“the book you were looking for.” Hence, the definite article the is required.
• Grammatical rule involved (English):
The definite article “the” is used before a noun when it refers to something specific or already identified, especially when followed by a defining clause (e.g., the book you were looking for).
• व्याकरण नियम (Hindi):
जब किसी संज्ञा से पहले ऐसा विवरण दिया गया हो जिससे वह विशेष/पहचानी हुई हो जाए, तो उसके पहले the का प्रयोग किया जाता है। यहाँ you were looking for उस पुस्तक को विशेष बना रहा है।
• Meanings / role of the other options:
• (b) No article: Incorrect because the noun is specific.
• (c) A: Used for non-specific singular nouns; not suitable here.
• (d) An: Used before vowel sounds; not applicable.
Thus, the correct option is (a) The.