\( { }^{\text {c) }} \log _{4} 16^{x} \)

To simplify \( \log_{4} 16^{x} \), we can break it down step by step. First, we realize that \( 16 \) can be rewritten as \( 4^{2} \). Hence, \( 16^{x} = (4^{2})^{x} = 4^{2x} \). Now, we substitute this back into the logarithm: \[ \log_{4} (4^{2x}) \] Using the property of logarithms that states \( \log_{b}(b^{a}) = a \), we can simplify this further: \[ \log_{4} (4^{2x}) = 2x \] So the result of \( \log_{4} 16^{x} \) is \( 2x \).