EMERGENCY-Need help with fill in the blank for Physics!!!

Which of the following correctly describes what happens when an atomic bomb explodes? small pieces of fissionable material are joined and form a body with a mass greater than the critical mass, the relative number of neutrons escaping decreases, and a chain reaction and explosion result. large pieces of fissionable matter are brought together quickly and form a body with a mass smaller than the critical mass, the relative number of escaping neutrons increases, and a chain reaction and explosion result.

Which compound is held together by the electrostatic force between two ions? a. co2 b. cci4 c. h2s d. mgf2

Sort the images based on whether there's a force of attraction or repulsion between the magnets shown. attraction repulsion