To evaluate the statements using rational approximations, let's analyze each one:
A. \(\sqrt{81} > 9\)
This statement is false because \(\sqrt{81} = 9\).
B. \(\sqrt{71} < \sqrt{61}\)
This statement is false. Since 71 is greater than 61, \(\sqrt{71}\) will be greater than \(\sqrt{61}\).
C. \(\sqrt{81} < 9\)
This statement is false because \(\sqrt{81} = 9\).
D. \(\sqrt{71} > \sqrt{61}\)
This statement is true. Since 71 is greater than 61, \(\sqrt{71}\) is indeed greater than \(\sqrt{61}\).
Thus, the true statement is:
D. \(\sqrt{71} > \sqrt{61}\).