SAT Question 1480dd5c: Linear Functions answer and explanation with Desmos solution

Choice B is incorrect. Substituting $1$ for $b$ in the given function yields $f\left(x\right)=4x+1$. For this function, when the value of $x$ is $7$, the value of $f\left(x\right)$ is $29$, not $28$.

Choice C is incorrect. Substituting $4$ for $b$ in the given function yields $f\left(x\right)=4x+4$. For this function, when the value of $x$ is $7$, the value of $f\left(x\right)$ is $32$, not $28$.

Choice D is incorrect. Substituting $7$ for $b$ in the given function yields $f\left(x\right)=4x+7$. For this function, when the value of $x$ is $7$, the value of $f\left(x\right)$ is $35$, not $28$.