"real numbers" is the biggest circle, which consists of the following: Rational, Irrational, integers, whole numbers, and finally natural numbers
These are called real numbers because they aren't imaginary, (√i)
You can imagine a bird house, Rational numbers is the house, the nest is the integers, the eggs in the nest are whole and the chicks inside the eggs are natural. Irrational is a squirrel, it doesn't belong in the birdhouse :)
Rational numbers: Are numbers that can be written as fractions, rationals contain integers, whole, and natural numbers ex: 1.5, 2, -5, etc.
1.33333 repeating does not count, since you can't write it as a fraction (This is a irrational number)
Integers: Are positive, negative, and zero. No fractions or decimals
ex: -5, 4, 3
They consist whole numbers and natural numbers
Whole numbers: No negative. All positive AND zero
ex: 1,3,0,100
They consist of natural numbers
Natural numbers: All positive and no zero
ex: 1,100,2,3,5
Irrational: Cannot be written as a fraction
ex: Pi, √3,√5
So the answer to this question is whole numbers
Hope this helped :) (I took quite a long time explaining)