Which of these fits gap 21?

Directions: Complete this passage by selecting the most suitable option for the corresponding gap.

Kangaroos are animals _____(21)______ only in Australia. They are called marsupial animals because they are the only mammals that _____(22)______ their young ones in a pouch outside their bellies. They are very powerful animals. Kangaroos _____(23)______strong and long hind legs. They use these to hop. They use their long and powerful tails to balance their bodies _____(24)_____ hopping.