#### Answer

$\left\{\sqrt{3}, \pi, \sqrt{12}\right\}$

#### Work Step by Step

RECALL:
Irrational numbers are numbers that cannot be expressed as a quotient of two integers a and b, where $b\ne0$.
Note that $\sqrt3$, $\pi$, and $\sqrt{12}$ cannot be expressed as $\dfrac{a}{b}$ where $a$ and $b$ are integers and $b\ne0$.
Thus, the elements of $A$ that are elements of the set of irrational numbers are:
$\left\{\sqrt{3}, \pi, \sqrt{12}\right\}$