Identify the sentence in which an adverb clause is underlined.

a. a garden snail may be the slowest animal of all.

b. although rabbits are small, they run faster than grizzly bears.

c. dogs such as greyhounds and whippets may reach top speeds of up to 40 miles per hour.

d. giraffes, which are animals with very long legs, can run a little faster than 30 miles per hour.