Question

Choose the correct answers from the alternatives given.
Which of the following is a true statement?
A. In all mammals, offspring develop within the female.
B. All mammals have hair and mammary glands.
C. All mammals are land-dwelling forms.
D. All of the above.

Answer 1

A mammal is a living creature that breathes air, has a backbone, and at some time in its existence grows hair. Mammals are among the most intellectual organisms on the planet. Mammals are a diverse group of creatures that encompass everything from cats to humans to whales.

Complete answer:
Option A: In all mammals, offspring develop within the female: this is an incorrect option because, in mammals, offspring do not develop within the female. The young develop within the female in viviparity, taking sustenance from the mother's blood via the placenta. The female's offspring develop and are born alive. Most mammals, certain cartilaginous fish, and a few reptiles are viviparous as a result of this.
Option B: All mammals have hair and mammary glands: Mammary glands generate milk, which mammals use to feed their young, unlike other vertebrates. Even though mammary glands are present in both men and females, most mammal species' mammary glands only completely mature in females, resulting in smaller nipples on males (including male humans). Additionally, all mammals have hair at some time in their lives. Not all animals live on land (dolphins).
Option C: All mammals are land-dwelling forms: Although some mammals are aquatic, some are airborne, and a few are “fossorial,” the bulk of mammals live on land (live underground). Many terrestrial animals live in trees and have longer limbs (and sometimes tails) to assist them to move from one tree to the next. so, this is the incorrect option.
Option D: All of the above: This is not a correct option because option A and option C are incorrect.

So, the correct option is Option B: 'all mammals have hair and mammary glands.

Note:
The majority of mammals are intelligent, with some having big brains, self-awareness, and the ability to utilize tools. Mammals use a variety of methods to communicate and vocalize, including ultrasonography, scent-marking, warning signals, singing, and echolocation. Mammals may form fission-fusion communities, harems, and hierarchies, but they also can be solitary and territorial. Although the majority of animals are polygynous, others are monogamous or polyandrous.