Given a scientific question, generate a correct answer to it.

Example Input: What kind of rock is gypsum?
Example Output: sedimentary

Example Input: The cytoplasm is all the contents of the cell inside the cell membrane, with the exception of what?
Example Output: nucleus

Example Input: What kind of bonds are forces of attraction between positive metal ions and the valence electrons that are constantly moving around them?
Example Output:
metallic bonds