Ascientist wants to prove that certain chemicals in cosmetics are likely to cause harm to developing fetuses, when used by a pregnant mother. what is the most likely limitation she will face in her scientific design?
a) limitations due to the time required to complete the experiment
b) limitations due to the system being too large to investigate thoroughly
c) limitations due to high expenses for equipment and supplies
d) limitations due to ethical concerns about experimental subjects

as soon as possible i am stuck