Question

1. the __ and __ of lighter elements fuse to form nuclei of much heavier elements. photons, neutrons protons, neutrons protons, nephrons electrons, proteins

Explanation:

In nuclear fusion, protons and neutrons (nucleons) of lighter elements combine. Photons are particles of light. Nephrons are functional units of kidneys. Proteins are biological macromolecules. Electrons are sub - atomic particles outside the nucleus.

Answer:

protons, neutrons