In a hypothetical system, the average computation spends $50\%$ of the total time using the CPU and the remaining $50\%$ waiting for I$/$O$.$

To achieve the best CPU utilization, $\_\_\_\_\_$ computations should run simultaneously. $(5$ points$)$

$2$

more than $2$

all available

The use of time$-$sharing will $\_\_\_\_\_.(5$ points$)$

speed up all computations

guarantee a reasonable response to each computation

improve resource utilization