Question

This golden ring is too (costly) to purchase.
a. Adverb
b. Adjective
c. Preposition
d. Conjunction​

Answer 1

Here the word costly is an Adjective.

Most of the adverbs end in ly, but there are some words like "costly" which end with ly but are adjectives rather than adverbs.

What are adjectives?

• The words that modify or describe the qualities of a noun or proper known are called adjectives.
• I brought new shoes. here the word new is an adjective.

What are adverbs?

• The words that give greater modification or description to adjectives and nouns are called adverbs.
• David chews loudly. Here the word loudly is an adverb.

So here the word costly will be an adverb.