Hi! I read the following question in a TOEIC book:
“Seasonal Affective Disorder

also known as
the winter blues, can do more than put a person in a bad mood. According to psychologists at the University of Chicago School of Medicine, the winter blues is a serious cyclical depression that can drastically affect a person’s work performance.
…
…
People with SAD begin to notice their moods ______ as soon as they start thinking about the onset of winter. For many people the symptoms of SAD are triggered as soon as the clocks go back an hour and we lose an hour of sunlight.
(A) changes
(B) changing(C) to change
(D) changed(Answer: B)” ((Longman Preparation Series for the New TOEIC Test, Advanced Course, 4th Edition, by Lin Lougheed, p. 163))
I think there is some reason that B (changing) is the ONLY correct answer, but I don’t know why D (changed) is wrong. (Grammatically, BOTH B (changing) AND D (changed) are correct. Idiomatically, B (changing) is correct and D (changed) is wrong in the above context, but I do NOT know the reason.) Is there anyone who can explain the reason? If there is, would you please help me?
Thanks in advance.