The correct answer is 1. Slowly and cautiously
Step-by-step explanation:
In grammar, the main function of an adverb is to modify a verb; this means, adverbs describe how an action occurs by answering to how, when, where, among others. Similarly, an adverb phrase modifies a verb but it is composed of two or more words.
According to this, in the sentence "Rita and Ron climbed slowly and cautiously up the steep staircase" the adverb phrase is "slowly and cautiously" because this set of words modify the verb "climbed" by explaining how this action occurred.