22. As shown in Figure 4, in the right triangle $\triangle ABC$, $AC=12, BC=5, \angle C=90^{\circ}$, inside the triangle, a semicircle $\odot O$ with its diameter on side $AC$ is tangent to $AB$. Then the radius $r$ of the semicircle is ( ).
(A) $\frac{7}{6}$
(B) $\frac{13}{5}$
(C) $\frac{59}{18}$
(D) $\frac{10}{3}$
(E) $\frac{60}{13}$
22. D.

Let the second tangent point of the semicircle $\odot O$ with $\triangle A B C$ be $D$. Then $O D \perp A B$.
Notice that, $\triangle A B C \backsim \triangle A O D$, and $A B=13$. Hence $\frac{r}{5}=\frac{12-r}{13} \Rightarrow r=\frac{10}{3}$.