Final answer:
The duty cycle for continuous wave ultrasound is 100 percent, which means the system emits ultrasound waves continuously without any breaks.
Step-by-step explanation:
The value of the duty cycle for continuous wave ultrasound is an important parameter in ultrasonography. The duty cycle is defined as the percentage of time that the ultrasound machine is actually emitting sound waves during one full cycle of operation.
For continuous wave ultrasound, the system is emitting ultrasound waves 100% of the time without any intervals of non-emission. Therefore, the correct answer to the question "What is the value of the duty cycle for continuous wave ultrasound?" is C. 100 percent.