Answer: Use M-mode instead of pulse-wave Doppler to measure the fetal heart rate.
Explanation: M-mode is a famous ultrasound process during the early days of Ultrasound technologies, M-mode has a very high sampling rate. One of the major disadvantages is that it may be difficult to align the M-mode to be the perpendicular to the SEPTUM. M-mode has only one (1) dimensional view of an object,to minimize the risk to the Fetus, M-mode is the most applicable tradeoff. Specifically, M-mode is mainly used because of its Axial and temporal resolution of the structure of objects.
One type is microwaves
Microwaves are used for radio and radar communications
Also used to cook food
"Light year" is a distance, not a speed. It's the distance light travels in one year, at the speed of 299,792,458 meters per second.