The Sound from Two Loudspeakers Is Received by a Microphone

Multiple Choice

The sound from two loudspeakers is received by a microphone at a point far away along the line through the speakers.The microphone registers maximum intensity when the speakers are 20 cm apart.The sound intensity decreases as the distance between the speakers is increased,reaching zero at a separation of 91 cm.If the distance between the speakers continues to increase,at what separation will the sound intensity again be a maximum?

A) 162 cm
B) 172 cm
C) 182 cm
D) 192 cm