Which of the following is not viviparous?

Which of the following mammals is adapted for aquatic life?

Given below are statements $X, Y,$ and $Z$ regarding the duck-billed platypus. Select the correct option based on these statements.
$X =$ It is an oviparous animal.
$Y =$ It has a four-chambered heart and the aortic arch curves to the right.
$Z =$ It is a mammal.

The zygomatic arch in the skull of a mammal $(rabbit)$ is formed by:

The renal portal system is absent in which of the following?

Which of the following animals does not have the ability to change its skin colour?