What is the time of flight in ultrasound imaging?

Choose only ONE best answer.

A
The duration it takes for an ultrasound post to travel from the transducer to an object and back as an echo
B
The time it takes for the ultrasound machine to start
C
The duration it takes for the sound waves to reach the body structures

A

The duration it takes for an ultrasound post to travel from the transducer to an object and back as an echo