Which of these includes an infinitive phrase functioning as an adverb?

Apply sunscreen thoroughly to avoid skin damage.
The purpose of sunscreen is to block harmful rays.
To be safe, apply sunscreen an hour before exposure
Do you really want to risk your health for a tan?

Question

Which of these includes an infinitive phrase functioning as an adverb?

Apply sunscreen thoroughly to avoid skin damage.
The purpose of sunscreen is to block harmful rays.
To be safe, apply sunscreen an hour before exposure
Do you really want to risk your health for a tan?

anonymous · Answer

An infinitive phrase begins with the word to and then a verb. All of these have those but which one is helping to describe a verb?

anonymous · Answer

Do you have any thoughts as to which is the right answer?