Which best explains the circulation system within mammals?
a. mammals use a closed, single-loop circulatory system aided by a three-chambered heart.
b. mammals use a closed, single-loop circulatory system aided by a four-chambered heart.
c. mammals use a closed, double-loop circulatory system aided by a four-chambered heart.
d. mammals use an open, double-loop circulatory system aided by a four-chambered heart.

Type the correct answer in the box. use numerals instead of words. fiona has a lovely flower bed in her yard. she wants to add a fence along one side of the flower bed. the fence material is sold in meters. fiona knows that her flower bed is 200 centimeters in length. how much fencing material does fiona need in meters? fiona needs meters of fencing material for her flower bed.

The organelle pictured is found in cells of and is theorized to have once been an independent organism.

3points hurry! what is the relationship between biotechnology, sharkskin, and disease resistance? bioengineers have developed an artificial sharkskin that does not allow resistant bacteria to grow on it. disease-causing microbes have been genetically modified to keep them from infecting the skins of sharks. scientists have created a device that can be attached to the skins of sharks that dramatically increases their abilities to resist disease. sharkskin produces many chemicals that can be collected and used to create antibiotics.