Dr White Reads About a New Theory That States That

Multiple Choice

Dr. White reads about a new theory that states that depression is caused by increased levels of estrogen in the womb. To test this theory, she conducted a study comparing the level of estrogen in amniotic fluid in individuals who were later diagnosed with depression with the level of those who did not develop depression. Dr. White found no differences between the groups in estrogen levels in the amniotic fluid.
Based on these results, Dr. White should conclude that:

A) she has disproved the previous theory.
B) her study was probably flawed in some way.
C) previous studies that support the theory are probably flawed.
D) there may be factors influencing the results that haven't yet been examined that contributed to the results of studies on this topic.