The difference between the apparent frequency of a source of sound as perceived by an observer during its approach and recession is 2% of the natural frequency of the source. If the velocity of sound in air is 300 m/sec, the velocity of the source is (It is given that velocity of source

• A.            6 m/sec                                  
• B.            3 m/sec
• C.            1.5 m/sec                               
• D.            12 m/sec