Dr. garcia is conducting an experiment to see how caffeine affects a person's brain activity. she asks ten test subjects to drink a cup of tea and tells them that there is caffeine in it. she then monitors their brain activity with a scanning device as they read from a book.

why should dr. garcia give some test subjects tea that doesn't have caffeine in it?
a.
because some of her test subjects don't like caffeine and don't want to drink it

b.
because some test subjects will guess the goal of her experiment and behave differently as a result

c.
because caffeine is not an important part of her experiment

d.
because she is interested in finding out how good or bad the tea tastes, not how it affects the test subjects