Answer: the correct answer is D) The set of natural numbers.
A set that contains infinite number of elements is called as infinite set.
Natural numbers are those that start from one and go till infinity. Thus, set of natural number is infinite as this set contains infinite number of elements, satisfying the property of infinite set.
On the contrary, option A), B), and C) contains finite numbers, which can be counted. Thus, they are not the example of infinite set.
Thus, D) is the right answer.