Ten-year-old Bill is playing with his baby sister, Lucy. He takes Lucy's teddy bear and hides it behind a pillow while Lucy watches. Lucy quickly finds the bear. Then Bill puts the teddy bear in a bag, puts the bag behind a chair (where he dumps out the bear), and brings out the empty bag. Lucy looks inside the bag but never tries to look for the bear behind the chair. Which one of Piaget's sensory motor substages is Lucy in

Which are observations about the tree on the right ,? check all that apply

Identify the missing parts of the carbon cycle

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.