\begin{tabular}{|l|l|}\hline 1.1 & Which number is undefined? \\ & A. \( \frac{0}{8} \) \\ B. \( \sqrt{8} \) \\ C. \( \sqrt{-8} \) \\ D. \( \frac{8}{1} \)\end{tabular}

The answer is C. \( \sqrt{-8} \). In mathematics, you can't take the square root of a negative number within the realm of real numbers, which makes it undefined in that context. However, if you step into the world of complex numbers, you can express it as \( 2i\sqrt{2} \) where \( i \) is the imaginary unit. Interestingly, this aspect of square roots is a gateway to the fascinating universe of complex numbers! These numbers, which combine a real part and an imaginary part, have applications that are fundamental in engineering, signal processing, and even quantum physics. So, while \( \sqrt{-8} \) may be undefined in the real world, in complex scenarios, it opens up a whole new dimension!