Which of the following is a vector in null A, where $A=\begin{bmatrix}3&4\\6&8\\\end{bmatrix}$

Question

Which of the following is a vector in null A, where $A=\begin{bmatrix}3&4\\6&8\\\end{bmatrix}$

$$\begin{bmatrix}4&-3\end{bmatrix}^T$$ $$\begin{bmatrix}2&2\end{bmatrix}^T$$ $$\begin{bmatrix}-1&1\end{bmatrix}^T$$ $$\begin{bmatrix}3&-4\end{bmatrix}^T$$

I was wondering is there a certain formula on how to solve this.I'm reading my textbook under the subspaces and spanning but i cannot find any example relating to this question