Which states the sequence of contractions in one heart beat? A)
left atrium and left ventricle together, pause, right atrium and right ventricle together
B)
left atrium, left ventricle, right atrium, right ventricle, pause
C)
right atrium and left atrium together, right ventricle and left ventricle together, pause
D)
right atrium, right ventricle, left atrium, left ventricle, pause

How are carbon dioxide emissions affecting the earths natural cycle of temperature change? plz apex

Use the drop-down menu to match the following definitions to the corresponding terms. the total variety of organisms that live in the biosphere a group of organisms that breed and produce offspring that can breed all of the biotic and abiotic factors in an area

Which is an advantage of having memory cells when a pathogen is encountered for a second time. a) the memory cells are what proliferate into clones of cells in response to the binding of an antigen. b) memory cells are vital to the primary immune response in that they immediately recognize pathogens even at the first encounter. c) memory cells are essentially effector cells that are short lived and attack antigens even without having a receptor specific to that antigen. d) it ensures that more lymphocytes with a receptor specific to a particular antigen will be present than in a host that had never encountered that pathogen.