Answer
(a) is correct.
Work Step by Step
The true weight of the suitcase is $mg=10\times9.8=98N$
When the elevator accelerates upward, normal force $F_N$ exceeds the true weight $mg$, as shown in Newton's 2nd law below: $$F_N-mg=ma$$ $$F_N=m(g+a)$$
Since $F_N$ is the value registered at the scale, $120N$ would be expected here.
In contrast, when the elevator accelerates downward, normal force $F_N$ is smaller than the true weight $mg$, as shown in Newton's 2nd law below: $$mg-F_N=ma$$ $$F_N=m(g-a)$$
So the scale will read $75N$ here.
Therefore, (a) is correct.
