Answer:
C
Explanation:
Electromagnetic waves travel at the speed of light and do not require molecules (gas, solid or liquid) to vibrate and travel.
Soundwaves when singing or from thunder vibrate particles to reach our ears and are known as mechanical waves.
Answer: It depends on the element.
Explanation: Every element has a different amount of protons in its nucleus. It is the same as its atomic number on the periodic table. For example: Hydrogen has an atomic number of 1 because it has 1 proton in its nucleus, Helium has 2, Carbon has 6, Platnium has 78, and so on...
You did not include the list but F is fluorine. The first halogen.
So, you can expect that the other members of the same group (halogens, column 17 of the periodic table) exhibit similar chemical behavior (reactivity).
So, I am sure your list contains one or more of theses elements: Cl (chlorine), Br (bromine), and I (iodine).
All of them you can expect to also be reactive non metal.
