Answer: Phrase
Explanation:
To be able to answer this, we need to know the difference between a clause and a phrase.
A clause simply refers to the group of words which has both a subject and the verb. An example of a close is "He laughed"
On the other hand, a phrase simply refers to the group of words without the subject and the verb.
In this case "walk carefully" is a phrase and not a clause as it doesn't have a subject.
