A hiker is attacked by a bear. What is this an example of?
Probable expected answer:
This could be an example of a "third person, present tense" sentence, but I think it is likely intended to be an example of the "passive voice".
For a sentence in the "passive voice" the subject, in this case "A hiker" is the recipient of the verb action. Contrast this to a sentence in the "active voice": A bear attacked a hiker