23. Lone Star geyser trail is one of the easiest five mile roundtrip hikes in Yellowstone. This mostly _______ trail follows an old service road along the Firehole River through unburned forests of lodgepole pine. Lone Star geyser erupts approximately every three hours, and is a crowd pleaser. This trail can also be accessed by bicycle with the final approach to the geyser _______ foot. (A) flat; in (B) rocky; by (C) level; on
(D) bumpy; off