Answer:
The correct option A.
Explanation:
Total numbers of students = 24.
Number of boys = 10
Number of girls = 24 - 10 = 14
Jeff claims that the ratio of boys to girls in this class must be 5:12.
The ratio of the number of boys to the total number of students is

Therefore Jeff found the ratio of the number of boys to the total number of students.
The ratio of boys to girls in this class is

Therefore the ratio of boys to girls in this class is 5:7.
Option A is correct.