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

Input: Consider Input: Passage: An atom's protons and electrons carry electrical charges. Protons, with their positive charge, are designated p+. Electrons, which have a negative charge, are designated e. An atom's neutrons have no charge: they are electrically neutral. Just as a magnet sticks to a steel refrigerator because their opposite charges attract, the positively charged protons attract the negatively charged electrons. This mutual attraction gives the atom some structural stability. The attraction by the positively charged nucleus helps keep electrons from straying far. The number of protons and electrons within a neutral atom are equal, thus, the atom's overall charge is balanced. Answer: neutrons

Output: What part of an atom is electrically neutral?

Input: Consider Input: Passage: the fact that stars are made up of very lightweight hydrogen gas. Answer: hydrogen

Output: What type of gas are stars made up of?

Input: Consider Input: Passage: We can see rainbows because they are formed by visible light. Visible light includes all the wavelengths of light that the human eye can detect. It allows us to see objects in the world around us. Without visible light, we would only be able to sense most objects by sound or touch, and we would never see rainbows. Like humans, most other organisms also depend on visible light, either directly or indirectly. Many animals use it to see. All plants use it to make food in the process of photosynthesis. Without the food made by plants, most other organisms could not survive. Answer: visible light
Output: What helps us see rainbows in the sky?