Answer
$\textbf{(a)}$ It is twice as much.
$\textbf{(b)}$ The best explanation is $\textbf{I}$.
Work Step by Step
$\textbf{(a)}$ It is twice as much. The drop time is the same, while the horizontal component of the Driver $2$ is twice as big and both of them are constant and we know that distance covered in that case equals velocity multiplied by time.
$\textbf{(b)}$ According to what is said in part $\textbf{(a)}$, the best explanation is $\textbf{I}$.
