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

The cardiovascular system in the human body consists of the heart, a network of blood vessels, and blood.
Which system in the human body consists of the heart, a network of blood vessels, and blood?

A(n) gastropods is noted for having its eyes at the tips of stalks or tentacles that emerge from its head.
What type of creature is noted for having its eyes at the tips of stalks or tentacles that emerge from its head?

The nuclear envelope is a double-layered plasma membrane like the cell membrane, although without membrane proteins.
The nuclear envelope is a double-layered plasma membrane like the cell membrane, although without what?