Which animal has very low metabolic rates and a quarter of the muscle tissue of animals of similar size, and whose hair grows in a direction opposite to that of its extremities?

Option C

Sloths are a group of arboreal neotropical xenathran mammals, constituting the suborder Folivora. Noted for slowness of movement, they spend most of their lives hanging upside down in the trees of the tropical rain forests of South America and Central America.

Sloths can be 60 to 80 cm (24 to 31 in) long and, depending on species, weigh from 3.6 to 7.7 kg (7.9 to 17.0 lb). Two-toed sloths are slightly larger.^[Sloths have long limbs and rounded heads with tiny ears. Three-toed sloths also have stubby tails about 5 to 6 cm (2.0 to 2.4 in) long.

sloths have colour vision, but have poor visual acuity. They also have poor hearing. Thus, they rely on their sense of smell and touch to find food.

Sloths have very low metabolic rates (less than half of that expected for a mammal of their size), and low body temperatures: 30 to 34 °C (86 to 93 °F) when active, and still lower when resting. Sloths are heterothermic, meaning their body temperature may vary according to the environment, normally ranging from 25 to 35 °C (77 to 95 °F), but able to drop to as low as 20 °C (68 °F), inducing torpor.

The outer hairs of sloth fur grow in a direction opposite from that of other mammals. In most mammals, hairs grow toward the extremities, but because sloths spend so much time with their limbs above their bodies, their hairs grow away from the extremities to provide protection from the elements while they hang upside down.