A mass $M$ is suspended by a rope from a rigid support at $A$ as shown in figure. Another rope is tied at the end $B$ and it is pulled horizontally with a force $F$. If the rope $A B$ makes an angle $\theta$ with the vertical, then the tension in the string $A B$ is
(a) $F \sin \theta$
(b) $F / \sin \theta$
(c) $F \cos \theta$
(d) $F / \cos \theta$