Given a scientific passage and an answer, generate a question for the given answer.

[Q]: Passage: Mouth Brooding. Some species of fish carry their fertilized eggs in their mouth until they hatch. This is called mouth brooding. If you look closely, you can see the eggs inside the mouth of the cardinalfish pictured here. Answer: mouth brooding
[A]: Some species of fish carry their fertilized eggs in their mouth until they hatch; this is called what?

[Q]: Passage: According to the cell theory , all living things are made up of cells, which is the structural unit of living organisms, and living cells always come from other living cells. In fact, each living thing begins life as a single cell. Some living things, such as bacteria, remain single-celled. Other living things, including plants and animals, grow and develop into many cells. Your own body is made up of an amazing 100 trillion cells! But even youlike all other living thingsbegan life as a single cell. Answer: trillions of cells
[A]: What is your body made up of?

[Q]: Passage: Summary Subatomic particles of the nucleus (protons and neutrons) are called nucleons. Anuclide is an atom with a particular number of protons and neutrons. An unstable nucleus that decays spontaneously is radioactive, and its emissions are collectively called radioactivity. Isotopes that emit radiation are calledradioisotopes. Each nucleon is attracted to other nucleons by the strong nuclear force. Stable nuclei generally have even numbers of both protons and neutrons and a neutron-to-proton ratio of at least 1. Nuclei that contain magic numbers of protons and neutrons are often especially stable. Superheavy elements, with atomic numbers near 126, may even be stable enough to exist in nature. Answer: nucleons
[A]:
What are subatomic particles of the nucleus called?