An ultrasound can produce the image of a fetus by using waves that are labeled as "ultrasound waves" or in ultrasonic frequency.
This may seem like an odd concept but you should note that everything we see and hear is made up of waves, like light and sound, that are at different frequencies.
The reason why there are different color lights are because there are different type of frequencies. Some frequencies, such as ultrasonic, we can not see with our human eye.<span />
Answer:
extant; extinct.
Explanation:
A species is a group of individuals that can interbreed to produce fertile and viable progeny. A species may be present on the earth and is surviving or may not be present now on the earth and have become extinct due to one or more reasons. Extant species are the species living on the earth in the present time while extinct species do not exist now. For instance, <em>Plateosaurus engelhardti</em> is a species of dinosaurs that survived on the earth during the Triassic period but does not exist now. On the other hand, <em>Homo sapiens, Apis indica</em> are some of the examples of the extant species that are surviving on the earth.
The limbic system helps control the emotion center of the brain
