Which statement best explains why each river has its own set of characteristics? Rivers flow downhill, pulled by gravity toward the sea.
Rivers interact with the ecosystems through which they pass.
Rivers absorb oxygen from the atmosphere as they flow downhill.
Rivers have climates that are determined by the biomes they flow through.

Once a woman attains puberty, her overuse mature and release one egg per ovarian cycle. which hormone stimulates this event?

What are the formed elements (cell or parts of cell) in blood and what are their functions ?

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.