What should be added to 5021 so that it may become a perfect square?  Choose the correct choice from the following choices.
A) 20
B) 23
C) 26
D) 27
E) 29
71x71=5041   5041-5021= 
<gadget id="calculator">5041-5021</gadget>
<output>20</output>
20   If added to 20 get perfect square   answer=20
<result>A</result>
What should be added to 5021 so that it may become a perfect square?