Alcohol nào sau đây là alcohol bậc I?

$\text{C}\text{H}{}_3-\text{C}\text{H}(\text{O}\text{H})-\text{C}\text{H}{}_3$.

$\left(\text{C}\text{H}{}_3\right){}_3\text{C}-\text{O}\text{H}$.

$\text{C}\text{H}{}_3-\text{C}\text{H}{}_2-\text{C}\text{H}{}_2-\text{O}\text{H}$.

$\text{C}\text{H}{}_3-\text{C}\text{H}(\text{O}\text{H})-\text{C}\text{H}{}_2-\text{C}\text{H}{}_3$.