What is the negation of the statement: 6 is irrational?

Question

$\begin {array} {1 1} (A)\;6 \: is\: even \: number & \quad (B)\;6\: is\: rational \\ (C)\;6\: is\: not\: irrational & \quad (D)\;6\: is\: odd \: number \end {array}$