Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

The location of an object in a frame of reference is called position.
The location of an object in a frame of reference is called what?

Once a plant cell becomes specialized, divide can they no longer do.
Once a plant cell becomes specialized, what can they no longer do?

Deep currents are caused by differences in density at the top and bottom of the ocean.

What is caused by differences in density at the top and bottom of the ocean?