Select the option that is related to the third number in the same way as the second number is related to the first number.
9 : 121 :: 7 : ?
The logic here is
$$121=11^2=\left(9+2\right)^2$$
The first and second number are in the form of $$n:\left(n+2\right)^2$$.
Similarly,
The fourth number =Â $$\left(7+2\right)^2$$ = 81
$$\therefore\ $$81 is related to 7 in the same way 121 is related to 9.
Hence, the correct answer is Option A
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