A rational number is any number that can be expressed as a fraction of two integers, where the denominator is not zero.
Now, let's analyze each option:
A. 7.8 - This can be expressed as \( \frac{78}{10} \), which is a fraction of two integers. So, it is a rational number.
B. \( \frac{8}{\sqrt{8}} \) - We can simplify this: \[ \frac{8}{\sqrt{8}} = \frac{8}{2\sqrt{2}} = \frac{8 \cdot \sqrt{2}}{2 \cdot 2} = \frac{4\sqrt{2}}{2} = 4\sqrt{2} \] Since \( \sqrt{2} \) is irrational, \( 4\sqrt{2} \) is also irrational. So, this is NOT a rational number.
C. ... (This option seems to be incomplete and cannot be evaluated.)
D. \( \sqrt{7} \) - The square root of a non-perfect square (like 7) is irrational. Thus, \( \sqrt{7} \) is NOT a rational number.
From the options given, A. 7.8 is the only rational number.
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