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

A human cannot survive the loss of the liver of the following.
A human CANNOT survive the loss of which of the following?

Gabbro is a dark dense rock that can be found in the oceanic crust.
Gabbro is a dark dense rock that can be found in what?

Cnidarians class of animal, including hydras and jellies, is considered the simplest to contain a nervous system.

What class of animal, including hydras and jellies, is considered the simplest to contain a nervous system?