Choose the most appropriate word to fill in the blank.There are _____…

The correct answer is Option (4) → fewer

Fewer and less:

• Fewer (the comparative of few) is used with countable plural nouns: fewer rooms, fewer books.
• Less (the comparative of little) is used with uncountable nouns: less water, less time.
• This sentence: "rooms" can be counted, and "than" calls for a comparative, so "fewer rooms" is correct.
• Two-step check: 1. countable or not: "rooms" is countable, so few/fewer; 2. degree: "than" needs the comparative, so "fewer".
• Complete sentence: There are fewer rooms in the new guest house than in the older one.
  Example: This year fewer students joined the drama club.

Why the Other Options are Incorrect?

Option 1: less — Incorrect. Less goes with uncountable nouns; "rooms" is a countable plural.
Example: Please add less sugar to my tea.

Option 2: lesser — Incorrect. Lesser means smaller in importance or degree and comes before a noun; it is not used with "than" for number.
Example: He chose the lesser of the two evils.

Option 3: few — Incorrect. Few is the positive form; it cannot be followed by "than".