Under Inland Rule 18, a vessel engaged in fishing when underway is required to keep out of the way of which vessel type?

Why C is correct

33 CFR §83.18(c) states that a vessel engaged in fishing when underway shall, so far as possible, keep out of the way of a vessel not under command and a vessel restricted in her ability to maneuver. A vessel engaged in fishing is not required to keep out of the way of power-driven vessels or sailing vessels under Rule 18; those vessel types must keep clear of the fishing vessel.