The Superposition of Two Waves $$y _ { 1 } = ( 0.006 \mathrm {~cm} ) \cos \left[ 2 \pi \left( \frac { 156 } { \mathrm {~s} } t \right) \right]$$

The superposition of two waves $$y _ { 1 } = ( 0.006 \mathrm {~cm} ) \cos \left[ 2 \pi \left( \frac { 156 } { \mathrm {~s} } t \right) \right]$$ and $$y _ { 2 } = ( 0.006 \mathrm {~cm} ) \cos \left[ 2 \pi \left( \frac { 150 } { \mathrm {~s} } t \right) \right]$$ at the location x = 0 in space results in

A) beats at a beat frequency of 3 Hz.
B) a pure tone at a frequency of 153 Hz.
C) a pure tone at a frequency of 156 Hz.
D) beats at a beat frequency of 6 Hz in a 153 Hz tone.
E) a tone at a frequency of 156 Hz,as well as beats at a beat frequency of 6 Hz in a 153 Hz tone.