Answer:
A: 12
Step-by-step explanation:
An Irrational Number is a real number that cannot be written as a simple fraction. (Irrational means not rational).
Therefore, we can immediately discount C as 1/42 is a rational number by inspection.
[tex]4.2=\frac{4.2}{1} =\frac{4.2}{1} \times \frac{10}{10} =\frac{42}{10}=\frac{21}{5}[/tex] so similarly -4.2 = -21/5
So as B and D can also be written as rationals, they are not irrational.
Therefore, A is irrational.
