Jack's teacher has a box of objects. He asks each student to pull out an object and identify whether it is a mixture or a pure substance. Jack pulls out a piece of iron. What is this object and why is it a mixture or a pure substance? A. A mixture, because it is only composed of one thing B. A pure substance, because there are several things making up the object C. A mixture, because there are several things making up the object D. A pure substance, because it is only composed of one thing

They said i have got a sign of tuberculosis what should i do

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.

Explain how the number of similarities between the embryos from early stage to late stage is used as evidence of a common ancestry