The numbers in each set are related to each other in a certain way.
(2,8,100), (7,2,81), (4,7,?)

Based on the relationship among the numbers in the first two sets, select the number that can replace the question mark (?) in the third set.

Let's analyze the pattern in the given sets:
First set: (2,8,100)

Add the first two numbers: 2+8=10

Square the result: 10
2
=100

Second set: (7,2,81)

Add the first two numbers: 7+2=9

Square the result: 9
2
=81

Third set: (4,7,?)

Apply the same logic: 4+7=11

Square the result: 11
2
=121

Thus, the number that replaces the question mark is 121.