Which of the following is true about photosynthesis?
a) it is an exothermic reaction.
b) it is an endothermic reaction.
c) it produces carbon dioxide.
d) it occurs in animals.

atomic theory is
a) subject to change if new information is discovered.
b) a solution to the problem of differing isotopes.
c) unchangeable.
d) a descriptive table that lists all of the elements.

two nonmetals from group 16 are likely to form a(n)
a) metallic bond.
b) double bond.
c) ionic bond.
d) covalent bond.