The equation of simple harmonic motion may not be expressed as (each term has its usual meaning):

• A
  $x = A \sin(\omega t + \phi)$
• B
  $x = A \cos(\omega t - \phi)$
• C
  $x = a \sin(\omega t) + b \cos(\omega t)$
• D
  $x = A \sin(\omega t + \phi) + B \sin(2\omega t + \phi)$