Answer:
encountering a bear
Explanation:
A phrase that started with a gerund is considered as a gerund phrase. The gerund phrase serves as a noun. A gerund is a verb ended with "ing". In a sentence, gerund phrase always function as nouns and they are used as subjects, subject complements or subjects.
For example, in the sentence
"Encountering a bear and its cub could be dangerous, and hikers should be particularly cautious."
"Encountering a bear" is a gerund phrase which function as the subject of the sentence;
