Hedgehogs are mammals. Touching a hedgehog causes it to roll into a ball to protect itself. Which characteristics is it displaying?
A excretion and movement
B growth and sensitivity
c movement and growth
D movement and sensitivity

In the context of the neural impulse, which of the following is true about the depolarization of neuron membranes?

When coal has reached it hardest, darkest form, it is called select one: 0 a. sub-bituminous b. lignite c. bituminous d. antrhacite next page

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.