A company has a newsletter. In January 2018 , there were 1,300 customers subscribed to the

Choice B is correct. It's given that in January $2018$, there were $\mathrm{1,300}$ customers subscribed to a company's newsletter and for the next $24$ months after January $2018$, the total number of customers subscribed to the newsletter each month was $7\%$ greater than the total number subscribed the previous month. It follows that this situation can be represented by the equation $c=a{\left(1+\frac{r}{100}\right)}^m$, where $c$ is the total number of customers subscribed to the company's newsletter $m$ months after January $2018$, $a$ is the number of customers subscribed to the newsletter in January $2018$, and the total number of customers subscribed to the newsletter each month was $r\%$ greater than the total number subscribed the previous month. Substituting $\mathrm{1,300}$ for $a$ and $7$ for $r$ in this equation yields $c=\mathrm{1,300}{\left(1+\frac{7}{100}\right)}^m$, or $c=\mathrm{1,300}{\left(1.07\right)}^m$.

Choice A is incorrect. This equation represents a situation where the total number of customers subscribed each month was $93\%$ less, not $7\%$ greater, than the total number subscribed the previous month.

Choice C is incorrect. This equation represents a situation where the total number of customers subscribed each month was $70\%$, not $7\%$, greater than the total number subscribed the previous month.

Choice D is incorrect. This equation represents a situation where the total number of customers subscribed each month was $600\%$, not $7\%$, greater than the total number subscribed the previous month.