Vector space

Which vector is a zero vector in the vector space of $2 \times2$-matrices?

a) $\begin{pmatrix} 1 & 0 \\ 0 & 1 \end{pmatrix}$,

b) $\begin{pmatrix} 0 & 0 \\ 0 & 0 \end{pmatrix}$,

c) $\begin{pmatrix} 0 \\ 0 \end{pmatrix}$,

d) 0.