Which of the following statement(s) is/are correct regarding class Aves?

(i) The forelimbs are modified into wings and the hindlimbs generally have scales and are modified for walking, swimming or clasping the tree branches.

(ii) Heart is completely four-chambered.

(iii) They are warm-blooded (homoiothermous) animals i.e., they are able to maintain a constant body temperature.

(iv) They are oviparous and development is direct.