A rational number is any number that can be expressed as a fraction \( \frac{a}{b} \), where \( a \) and \( b \) are integers and \( b \) is not zero.
Let's analyze each option:
- \( \sqrt{7} \) – This is an irrational number.
- 7.8 – This is a rational number since it can be expressed as \( \frac{78}{10} \) or \( \frac{39}{5} \).
- \( \pi \) – This is also an irrational number.
- \( \frac{8}{\sqrt{8}} \) – While it can be simplified, \( \sqrt{8} \) is irrational, so this fraction is irrational as well.
Therefore, the only rational number among the given options is 7.8.