Which kingdom would include organisms that are all heterotrophic and motile?

Animalia, essentially

Explanation:

First, let's define our terms -

Heterotrophic: consumes other organisms to survive, as opposed to autotrophic

Motile: can move around, as opposed to sessile

There is debate on what constitutes a kingdom, but I generally go with the 6 kingdoms model, which includes animalia, plantae, fungi, protista, eubacteria, and archaebacteria.

Fungi, though heterotrophic, include mushrooms, which are obviously stationary (sessile). So we can rule them out.

Plantae are your traditional plants, which clearly fit neither of the categories, being sessile and phototrophic (they get energy from light, not other organisms.)

Archaebacteria are mostly autotrophs. I doubt they would be considered anyway.

Eubacteria, your traditional bacteria, include cyanobacteria, which are photosynthetic, and other exceptions. I don't think this is what the question is going for.

Protista are essentially the spare parts drawer of the kingdom system. They vary widely in being hetero- or autotrophic, so they certainly don't fit the criteria.

I can only conclude that this question is asking for animalia, which for the most part are heterotrophic and motile. (An exception is the most primitive, sponges or porifera, which are sessile and can't move around, but I expect this is what the question is looking for.) Because heterotrophy and motility are two defining features of animalia, most likely this is what the question is asking. This is a difficult question, because biologists themselves aren't real decided on the right answer.