which of the following are irrational numbers?

Explanation:

Step1: Recall the definition of irrational numbers

Irrational numbers cannot be written as a fraction $\frac{a}{b}$ where $a,b\in\mathbb{Z}$ and $b\neq0$.

Step2: Analyze 0

$0=\frac{0}{1}$, so it is rational.

Step3: Analyze $\pi$

$\pi$ has a non - repeating, non - terminating decimal expansion and cannot be written as a fraction, so it is irrational.

Step4: Analyze $\sqrt{9}$

$\sqrt{9} = 3=\frac{3}{1}$, so it is rational.

Step5: Analyze $\sqrt{49}$

$\sqrt{49}=7=\frac{7}{1}$, so it is rational.

Answer:

$\pi$ is the irrational number.