The correct option is D 12,000
Each smiling face represents 600 students.
There are 8 smiling faces in Alpha school.
So,
Number of students in Alpha school
= 600 × 8 = 4,800 students.
There are 5 smiling faces in Beta school.
So,
Number of students in Beta school
= 600 × 5 = 3,000 students.
There are 7 smiling faces in Gamma school.
So,
Number of students in Gamma school
= 600 × 7 = 4,200 students.
Total number of students in all the three schools together = 4,800 + 3,000 + 4,200 = 12,000