Answer:
the layer of the earth's atmosphere that contains a high concentration of ions and free electrons and is able to reflect radio waves. It lies above the mesosphere and extends from about 50 to 600 miles above the earth's surface.
Explanation:
Answer:
B
Explanation:
An undifferentiated cell is such as that in a blastocyte. They are multipotent and can differentiate into any type of cells. The cells of the mass begin to have their gene differentially expressed (due to differential silencing of particular genes) hence the cell become determined. They become well organized into tissue such as skin and other organs.
Answer:
a. both the aorta and pulmonary trunk
Explanation:
your welcome
It can last from 1 to 4 hours
