#### Answer

pure imaginary number;
nonreal complex number;
complex number

#### Work Step by Step

Simplify the given expression to obtain:
$=\sqrt{25(-1)}
\\=5\sqrt{-1}
\\=5i$
RECALL:
The complex number $a+bi$ is:
(i) a pure imaginary number when $a=0$ and $b\ne0$;
(ii) a real number when $b=0$;
(iii) a nonreal complex number when $b\ne0$.
The given expression is equivalent to $5i$. $5i$ has $a=0$ and $b\ne0$. Thus, it is a:
pure imaginary number;
nonreal complex number;
complex number