Question

Which of the following is equivalent to the expression below?

Answer 1

$i=\sqrt{-1}\\\\\\sqrt{a\cdot b}=\sqrt{a}\cdot\sqrt{b}$

$\sqrt{-20}=\sqrt{-1\cdot4\cdot5}=\sqrt{-1}\cdot\sqrt4\cdot\sqrt5=i\cdot2\sqrt5\\\\Answer:\ \boxed{A.\ 2i\sqrt5}$