Option C and D is correct .....
Answer:
Option A) Circle.
Step-by-step explanation:
We are given the equation:

A general equation of the circle is of the form:

where (h,k) is the center of the circle and r is the radius of circle.
Comparing the two equations, we get,

Thus, the given equation is equation of a circle centered at (3,12) and of radius 5 units.
1. x <= 31
2. x < 28
For number 1, x is less than or equal to 31 because the number of days in a month (represented by x) will be less than or equal to 31.
For number 2, x is less than 28 because the number of students (represented by x) in each class will always be less than 28.