When we say that an experiment is controlled, we mean that

a.
the outcome is certain

b.
the theory has already been supported

c.
there is only one theory being tested by the experiment

d.
there is only one difference between experimental groups

Which of these statements is true about autotrophs, but not heterotrophs? a. they use sugar and oxygen to make carbon dioxide and water.b. they use chlorophyll and oxygen to make carbon dioxide and water.c. they use sunlight, water, and carbon dioxide to make sugars.d. they use sunlight, water, and oxygen to make chlorophyll.