Choose from:
(1). ferns
(2). sugar
(3). bushes
(4). naked mole rats
(5). rocks
(6). ice cubes
(7). alpacas
(8). shrub beds

Fact 1: Some animals' fur grows thicker for staying warm in the winter. Fact 2: Alpaca fur is one of the softest furs in the world. Given the two facts above, what keeps itself warm naturally in the winter?
Answer:
(7).