An ideal square wave with period of 20 ms shown in the figure, is passed through an ideal low pass filter with cut-off frequency 120 Hz. Which of the following is an accurate description of the output?

• A. Output is zero
• B. Output consists of both 50 Hz and 100 Hz frequency components
• C. Output is a pure sinusoid of frequency 50 Hz
• D. Output is a square wave of fundamental frequency 50 Hz