Question

All plots must have _____. themes conflict action dialogue

Answer 1

All plots must have CONFLICT.

Themes are the broader ideas in a piece of work. And they are not specific to the plot. All plots must not have action, it can be other genres as well. All plots must not have dialogue, the plot can be entirely narrated.

On the other hand, a plot must have a conflict to define it and thereby develop it so that it catches the readers' eyes.