Question

What is the net force required to accelerate a 16 kg box at a rate or 1.4 m/s^2

Answer 1

You can use Newton's Second Law which states:
$\sum \vec{F} = m\vec{a}$

Plug in given information:
$\sum \vec{F}=16(1.4) = 22.4N$

This is closest to option b which is your answer.