Hi, thanks for your post. Yes, you can think of this question in that way.
Negating (D): Even if each step in a series of changes involves a decrease of one attribute (here, carbon) and an increase of another (here, hydrogen), that does not necessarily mean that the series will terminate with the first attribute eliminated (no carbon at all) and only the second attribute present (pure hydrogen).
The argument in the stimulus would thus fall apart.
Hope this helps! Please let us know if you have any additional questions.
