Answer:
Option B. 85
Step-by-step explanation:
Two sections of a class took the same quiz.
Mean score of section A of 15 students = 80
Mean score of section B of 20 students = 90
We will calculate the approximate mean score for all the students.
The pool mean is the mean of means of two or more groups. We will find it by this formula = 
= 
= 85
The approximate mean score for all the students on the quiz was 85.