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

Ovulation takes place in the ovary and is part of the menstrual cycle.
Ovulation takes place in what organ and is part of the menstrual cycle?

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?

Industry is the greatest source of hazardous waste.
What is greatest source of hazardous waste?