What can be changed to make the following sentence true?
The physical symptoms of psychophysiological disorders are nonexistent, and they can be produced or exacerbated by psychological factors.
a. The word "exacerbated" should be changed to the word "worsened."
b. The word "nonexistent" should be changed to the word "real."
c. The word "physical" should be changed to the word "psychological."
d. The word "psychological" should be changed to the word "physical."