Answer:
C. Infinitive.
Explanation:
To see an eagle soar in the air is an incredible sight. The verb to see is infinitive because the structure is always To + Verb and it is the way you find it in the dictionary. On the other hand, the gerund verbs are the ones that finish in - ING like, playing, cooking, watching, etc. And the participle verbs are used in the perfect tenses like, I have written a book, I had taken a shower, etc. Good luck!
