SAT Question cfff8f8e: Nonlinear Functions answer and explanation with Desmos solution

Choice B is correct. It's given that each day for five days after a social media channel posted a video, the number of subscribers doubled from the number the previous day. Since the number of subscribers doubled each day, the relationship between $n$ and $d$ can be represented by an exponential equation of the form $n=a{b}^d$, where $a$ is the number of subscribers at the time of posting the video and the number of subscribers to the channel increases by a factor of $b$ each day. It's given that at the time of posting the video, the channel had $53$ subscribers. Therefore, $a=53$. It's also given that the number of subscribers doubled, or increased by a factor of $2$, from the number the previous day. Therefore, $b=2$. Substituting $53$ for $a$ and $2$ for $b$ in the equation $n=a{b}^d$ yields $n=53{\left(2\right)}^d$.