When the activity level declines within the relevant range, what should happen with respect to the fixed and variable costs per unit?

Question $12$ options:

A$)$

The variable cost per unit increases and the fixed cost per unit doesn't change.

B$)$

Both the fixed and variable costs per unit increase.

C$)$

The fixed cost per unit increases and the variable cost per unit doesn't change.

D$)$

Neither the fixed nor variable costs per unit change.