Hi,
The answer should be letter C, since a compound is made of atoms of two or more elements, in a defined ratio, bonded together.
Answer:
all of them have seven valence electron
Gases are less dense and the molecules are farther apart which means that it can be compressed
The particles are no longer held together by the attractive forces keeping it a liquid (hydrogen bonds in the case of water). Enough energy has to be put into the system to break these bonds. When this happens the particles pull apart and fill the space available as a gas
I think cleavage , I could be wrong