Evaluate each statement for accuracy: Statement $1$ is true because flexible budgets can adapt to different levels of multiple cost drivers. Statement $2$ is false; variances depend on the relationship of costs to drivers, not just the number of drivers. Statement $3$ is misleading; the presence of multiple drivers does not preclude revenue or spending variances. Statement $4$ is generally true as more cost drivers can lead to more precise variance calculations.

Identify the combination of statements that validate the answer: Since statements $1$ and $4$ are true, they fit the criteria, while statements $2$ and $3$ are not entirely accurate.

Final answer: Both statements $1$ and $4$ are true.