This question requires evaluating the accuracy of three statements concerning modulation techniques and the types of amplifiers used in radio frequency (RF) transmitters.

Modulation Statement Verification

• Statement 1: "In low-level modulation, linear amplifiers are required in order to avoid any waveform distortion."
  • Low-level modulation occurs at low signal power before the final amplification stage.
  • To prevent distortion of the modulated signal during amplification, linear amplifiers (which maintain the signal's waveform shape) are essential.
  • Therefore, Statement 1 is correct.
• Statement 2: "High-efficiency class B amplifiers are used in high-level modulation."
  • High-level modulation takes place in the final power amplifier stage.
  • Class B amplifiers (and Class AB) are known for their higher efficiency compared to linear amplifiers like Class A.
  • Using high-efficiency amplifiers in the final stage is crucial for power conservation in high-level modulation systems.
  • Therefore, Statement 2 is correct.
• Statement 3: "In high level, modulation takes place in the last RF amplifier stage of the transmitter."
  • This statement describes the fundamental principle of high-level modulation, where the modulation process directly affects the output of the final RF power amplifier.
  • Therefore, Statement 3 is correct.

Overall Correctness Assessment

All three statements accurately describe aspects of low-level and high-level modulation, including the types of amplifiers and the stage where modulation occurs in the transmitter.