Consider the situation shown in diagram:

Observer hears sound from car directly and also after reflection from the wall. Choose the CORRECT statement(s):
 

If  $V_B=V_C=0$  , then beat frequency heard by observer is zero irrespective of  $V_A$ . 
 

If $V_A=0$ , beat frequency heard by observer is zero irrespective of  $V_B\&V_C$ . 
 

If  $V_B\ne 0$, observer will surely hear beat for any value of  $V_A\&V_C$. 
 

For $V_A=V_B=V_C$ , beat frequency heard by observer may be zero.