The correct answer is A. touch upon.
The verb "touch upon" means to discuss something briefly or in passing. In this context, the speaker is saying that the person they are talking about did not discuss the point in question at all. The other options are incorrect because they do not convey the same meaning.
- Option B, "touch on," is similar to "touch upon" but it implies a more in-depth discussion.
- Option C, "touch of," means to have a small amount of something.
- Option D, "No improvement," is incorrect because the sentence is grammatically correct and does not need to be changed.