A medium can be anything that a wave can pass through e.g the medium can be solid objects, air, water, etc.
An element or compound which occurs naturally in the earth is a mineral
The correct option is C.
A Lewis dot diagram is a representation of the valence electron of an atom, which uses dot around the symbol of the atom. Chlorine has seven electrons in its outermost shell, these seven electrons are arranged in form of dot around the atom of chlorine. If you count the number of dot given in option C, you will notice that they are seven.
Color change bubbles and i think dissolving
