Answer: Option B. unfavorable direct labor efficiency variance
Explanation:
From the scenario we can relate that when new workers were hired to replace the skilled workers who resigned, the profits fell 10%. This means the result is unfavorable. So we can cancel out the 1st and 4th options. Now, the workers were slow during their timing period this means that their efficiency was low. So this imparts that it is direct labor efficiency variance.
So option B. unfavorable direct labor efficiency variance is correct