A 33.33% duty cycle rectangular wave is fed to the input of an Spectrum Analyzer. What will be observed?

A

$$ 2^{nd}, 5^{th}, 8^{th} .............$$ harmonics missing

B

$$ 3^{rd}, 6^{th}, 9^{th} .............$$ harmonics missing

C

$$ 1^{st}, 4^{th}, 7^{th} .............$$ harmonics missing

D

All the harmonic present