Choose the sentence where 'high' is used as an adverb :-

Some birds fly high in the sky.

The correct answer is OPTION 2

The sentence where "high" is used as an adverb is: Some birds fly high in the sky.

Here's why:

• In "We must have high ambition," "high" modifies the adjective "ambition," making it an adjective.
• In "She had high hopes from his son," "high" modifies the noun "hopes," making it an adjective.
• In "Her confidence is high," "high" modifies the noun "confidence," making it an adjective.
• However, in "Some birds fly high in the sky," "high" modifies the verb "fly," telling us how they fly, making it an adverb.