Four different independent waves are represented by $(i)$ $y_1 = a_1 \sin \omega t$,$(ii)$ $y_2 = a_2 \sin 2\omega t$,$(iii)$ $y_3 = a_3 \cos \omega t$,and $(iv)$ $y_4 = a_4 \sin (\omega t + \frac{\pi}{3})$. With which two waves is interference possible?

• A
  In $(i)$ and $(iii)$
• B
  In $(i)$ and $(iv)$
• C
  In $(iii)$ and $(iv)$
• D
  Insufficient data to predict.