Answer:
Ionic bonds usually occur between metal and nonmetal ions. For example, sodium (Na), a metal, and chloride (Cl), a nonmetal, form an ionic bond to make NaCl.
Explanation:
The correct answer is "greenhouse gases." Certain gases in the atmosphere, like carbon dioxide, nitrous oxide, and methane, absorb heat and prevent it from escaping into space. These gases are called greenhouse gases.