How is an ultrasound scan for fetus (unborn baby) better than aX-ray?

Why should we not put a pin or pencil in our ears?

What type of scans are used these days to monitor the growth of developing baby in the uterus of the mother?

What is the name if the device which is used to find the depth of sea (or ocean) by using ultrasonic sound waves?

Write the full name of ‘SONAR’.