Tổng

Câu hỏi: Tổng $S=9+99+999+\dots +\underset{2018 chu so 9}{\underbrace{999...9}}$ bằng:

A. $\frac{{10}^{2018}-1}{9}$

B. $\frac{{10}^{2019}-1}{9}$

C. $\frac{{10}^{2018}-18163}{9}$

D. $\frac{{10}^{2019}-18172}{9}$