The correct answer is option 4: A is false but R is true.

In this question, the assertion (A) states that the mammals we see around do not hibernate. The reason (R) provided is that unlike other kinds of animals, mammals feed their young ones with milk.

Let`s analyze each option:

Option 1 states that both A and R are individually true and R is the correct explanation of A. However, this is not accurate. Although R is true, the assertion A is false as there are indeed mammals that hibernate, such as bears and bats.

Option 2 states that both A and R are individually true but R is not the correct explanation of A. This is the correct option. R is true as mammals do indeed feed their young ones with milk, but A is false as there are mammals that hibernate.

Option 3 states that A is true but R is false. This is incorrect, as A is false.

Option 4, the correct answer, states that A is false but R is true. This accurately reflects the relationship between A and R. A is false because there are mammals that hibernate, while R is true as mammals do feed their young ones with milk.