The following sentences all involve the verb "show" followed by a noun phrase. Number 6 sounds a bit weird, and the last one is just wrong — but why is that?
- The video shows the differences between them.
- The video shows them being different/the same.
- The purpose of the video is to show the differences between them.
- The purpose of the video is to show them being different/the same.
- The video shows the effects of smoking.
- The video shows smoking being unhealthy.
- The purpose of the video is to show the effects of smoking.
- The purpose of the video is to show smoking being unhealthy.
These are "grammatically correct", meaning they meet the expectation (as of now) of how verbs/nouns/etc go together. I'm interested in the reason why the two sound awkward. In particular, I want to know what it is that people expect to hear after "show" which distinguishes 6,8 from 2,4, for instance.