Which of the following is the largest mammal?

In which one of the following sets of animals do all the four give birth to young ones?

Which of the following is an oviparous mammal?

Sonar system is found in which of the following organisms?

Choose the correct option for the following statements:
$(i)$ Animals that maintain a constant body temperature are called $cold-blooded$ / $warm-blooded$ animals.
$(ii)$ Mammals are $viviparous$ / $oviparous$ animals.

Which of the following represents the correct match of a feature with the given animal?