Which of the following is not a real number?

Answer:
B
Step-by-step explanation:
if you put it in the calculator it says error. I was taught to only use positive numbers. for example √4
Answer:
[tex] \sqrt{ - 4} [/tex]
Step-by-step explanation:
Non real number are neither irrational numbers(
[tex] \sqrt{3} [/tex]
and rational numbers (-2 or 1/2)