Abiologist is studying blood vessels which have valves to prevent the backflow of blood. based on this information you would conclude that he or she is studying

The biologist is studying the atria and the ventricles of the heart. The heart is made up of four chambers; two atria upper chambers and two ventricles lower chambers. Each of the chamber has a valve through which the blood passes before existing the chamber. The valves prevent the blood from flowing backward.

Because the earth is not round ,but it may seem round when viewed from ,our planet but true some points earth is not round was an oblate spheroid -a square that it squashed as globe however is not even a perfect oblate spheroid.in fact isaac newton's first proposed that earth was not perfectly round but it was an oblate spheroid instead.that mean a square that is squashed as its poles and swollen at the