All the numbers in the Number System are classified into different sets and those sets are called as Number Sets.
The set of real numbers is divided into natural numbers, whole numbers, integers, rational numbers, and irrational numbers.

N= {1, 2, 3....} is the set of natural numbers.
(0, 1, 2, 3....} is the set of whole numbers.
I = {...-3, -2, -1, 0, 1, 2, 3...} is the set of integers.
The numbers 2/3,3/5, 10.3, 102.25, etc. are rational numbers but not integers.
etc. are irrational numbers.
A. 53
B. 0
C. 
D.
Correct Answer: A
Step 1: 0 is a whole number and an integer. [Whole numbers are {0, 1, 2, ...}, Integers are the set of whole numbers and their opposites.]
Step 2:
is a mixed number, which can be written in the form of rational number as
[A rational number is the ratio of two integers in the form a/b, where b ≠ 0.]
Step 3:
is a negative rational number.
Step 4: 53 is a natural number. [Natural numbers are {1, 2, 3, ...}.]
Step 5: 53 is an integer, a whole number and it can also be written in the form of rational number as 53/1.
Step 6: So, 53 is at once a rational number, an integer, a whole number, and a natural number.
Q1: Which of the following is both a rational number and an integer?
Q2: Which number set does 0 belong to, but not the natural numbers?
Q: Is 0 a natural number?
A: No, 0 is a whole number but not a natural number. Natural numbers start from 1.
Q: Are all fractions rational numbers?
A: Yes, as long as the numerator and denominator are integers and the denominator is not zero.