you'll want to be familiar with the definitions of each of the answer choices:
natural numbers are positive integers (so 1, 2, 3, etc)
whole numbers are just numbers without fractions (so, any integer)
integers are whole numbers, positive or negative
rational numbers can be written as a ratio (a fraction)
irrational numbers CAN'T be written as a ratio (so, like pi)
real numbers include all rational and irrational numbers
so, you see that a lot of these overlap. go through them and see what the number 5 can apply to. yes, it's a positive integer, so it's a natural number. yes, it's a whole number. yes, it's an integer. it's a rational number as well because it can be written as a ratio (5/1). it's also a real number, because real numbers include rational numbers.
the only set that DOESN'T contain 5 is irrational numbers. 5 can be expressed as a ratio, so it can't be irrational.
