Which of the following is $\textbf{not}$ TRUE?
(a) In a complete graph $K_n$ ($n$ $\geq$ $3$), Euler circuit exists $\Leftrightarrow$ $n$ is odd.
(b) In a complete bipartite graph $K_{m,n}$ (m $\geq$ 2 and n $\geq$2), Euler circuit exists $\Leftrightarrow$ m and n are even.
(C) In a cycle graph $C_n$($n \geq$3), Euler circuit exits for all $n$
(d) In a wheel graph $W_n$ ($n \geq 4$), Euler circuit exits $\Leftrightarrow$ $n$ is even.