A source and an observer are moving towards each other with a speed equal to \[\frac{v}{2}\] where \[v\] is the speed of sound. The source is emitting sound of frequency n. The frequency heard by the observer will be [MP PET 2003]

• A.            Zero                                         
• B.            \[n\]
• C.            \[\frac{n}{3}\]                     
• D.            \[3n\]