Answer: The correct option is (a) A.
Step-by-step explanation: The given graph shows y as a function of x.
We are to select the segment in which the function is a constant.
The function will be constant in a segment means whatever may be the value of x in that segment, the value of y remains constant.
We can clearly see in the given graph that
except the segment A, in all other segments B, C and D, the value of y is changing with the value of x.
Only in segment A, the value of y remains same throughout the segment irrespective of the value of x.
Thus, in segment A, the function y is constant.
Option (a) is CORRECT.