$\mathop {\lim }\limits_{x \to 0} \frac{\left(7^x-1\right)^4}{\tan \left(\frac{x}{\mathrm{k}}\right) \cdot \log \left(1+\frac{x^2}{3}\right) \cdot \sin 4 x}=3(\log 7)^3$, then $\mathrm{k}=$
- A$\quad 4(\log 7)^{-1}$
- B$\frac{1}{4}(\log 7)^{-1}$
- C$\quad 4 \log \left(\frac{1}{7}\right)$
- D$\frac{1}{4} \log 7$
✓ Correct answer: A
Want the full step-by-step reasoning?