We are asked to differentiate \( \log x^{100} \). Using the logarithmic property \( \log a^b = b \log a \), we can rewrite the expression as:
\[
\log x^{100} = 100 \log x.
\]
Now, differentiating \( 100 \log x \) with respect to \( x \) gives:
\[
\frac{d}{dx} (100 \log x) = \frac{100}{x}.
\]
Thus, the correct answer is option (C) \( \frac{100}{x} \).