Which sentence uses an infinitive as an adjective?

a) to become an engineer has always been a dream of mine.
b) sally tried to play the guitar, but she became a singer instead.
c) fred was a serious soccer player and was determined to win each game.
d) the best way to learn to make biscuits is to talk to my mom.

Which sentence uses an infinitive as an adjective?

D) The best way to learn to make biscuits is to talk to my mom.

This sentence uses the infinitive to learn as an adjective.

technical documents should be clear and precise. basically, clarity is the key element in a successful technical document.

i literally just read the book and studied it for months so i could you, but i need to know where these questions are coming from. they are too general.