Which of the following is a rational number?
A) $\sqrt { 2 } + 1$
B) $2 \sqrt { 2 } - 1$
C) $\frac { 1 } { \sqrt { 2 } }$
D) $\frac { \sqrt { 2 } } { \sqrt { 2 } + 1 }$
E) $\frac { 2 \sqrt { 2 } - 2 } { 3 \sqrt { 2 } - 3 }$

A note that Elif read in her mathematics book states that $\sqrt{a} + \sqrt{b} = \sqrt{c}$ for some values. Because water dripped on her book, Elif could not read the number $b$ in the example.
Accordingly, which of the following cannot be the number $b$?
A) $\sqrt{5}$
B) $\sqrt{20}$
C) $\sqrt{45}$
D) $\sqrt{60}$
E) $\sqrt{80}$