Answer:
d) 50
Explanation:
The frequency, that in this case means absolute frequency, means the total amount of subjects that vote for each candidate (not the proportion, that would correspond to the relative frequency).
If the distribution is uniform and we have 3 categories or classes, the three of them should have the same frequency.
The sample size is: 40+60+50=150.
If we have 3 classes, and the distribution is uniform, we should have a frequency for each class of 150/3=50.