What are the three parts of the cell body theory?

In which situations is the principle of cross-cutting relationship useful in determining relative age?

Astudent is looking through a microscope at some cells of an onion root tip. many of these cells are undergoing division since the root tip grows quickly and requires more cells. which cell most recently underwent metaphase? w x y z

Which of these substances does not protect against invaders in the nonspecific immune response? a. saliva b. mucus c. tears d. urine