Products have different or than the reactants. (there are two correct answers select both.)

select one or more:
a. chemicals
b. atoms
c. properties
d. behaviors

the mass of the reactant has to be the as the mass of the product.
select one
a. same
b. different

Many birth-control pills release a constant amount of synthetic estradiols and progesterone for 21 days. true or false

How do you suppose living conditions differ between the country furthest along in the demographic transition compared to the country earliest in the transition? how would living conditions in these two countries affect both birth and death rates?

Cancer cells spread to other parts of the body by entering the bloodstream. which of the following organs could prevent a cancer cell in the bloodstream from spreading, and why? a. the spleen, because it releases lymphocytes into the blood b. the peyer's patches, because they release lymphocytes into the blood c. the lymph nodes, because they release lymph into the blood d. the thymus, because it releases lymph into the blood