If $\frac{a}{b}=\frac{a}{b}$ then $\frac{b}{a}$ is called

$\frac{b}{a}$ is called the multiplication inverse of $\frac{a}{b}$  Hence$\frac{a}{b}\times \frac{b}{a}=1$ . So $\frac{b}{a}$ is not additive inverse of $\frac{a}{b}$ and also

$\frac{a}{b}=\frac{a}{b}\Rightarrow \frac{a}{b}+\left(\frac{-a}{b}\right)=0$

So , $\frac{-a}{b}$ is additive inverse of $\frac{a}{b}$

But here asked about $\frac{b}{a}$

B: Since$\frac{a}{b}\times \frac{b}{a}=1$ . Clearly  says that $\frac{b}{a}$ is multiplicative inverse of $\frac{a}{b}$