B 
A circle is centered at $O$, $AB$ is a diameter and $C$ is a point on the circle with $\angle COB=50^{\circ}$. What is the degree measure of $\angle CAB$? 
Options:
A: $$20$$ 
B: $$25$$ 
C: $$45$$ 
D: $$50$$ 
E: $$65$$ 