Question 4. Select the statement that best describes the PM wave. a. Carrier phase angle changes represent the PM modulated signal, however, unlike FM and AM modulated carriers, it is not always easy to see these phase changes in the plot. b. The FM signal accurately represents the message. c. Although PM and FM techniques are classified as angular modulation techniques, they cannot be used interchangeably (i. e., modulated with FM and demodulated with PM, and visa versa). d. All statements are correct.