Gravity because the earth's gravity is what's causing it to orbit it
Answer:
D. The particles move up and down without changing their position
Explanation:
These are gases. They are typically known for their randomness and no fixed arrangement of their atoms.
Gases generally assume the volumes of the containers they fill. They spread easily and readily to fill the volume where they occupy. Also, gases are readily compressible as they lack intermolecular attraction between their molecules.
NH3 is a molecule with a nitrogen atom in the middle surrounded by 3 hydrogen atoms bonded covalently. Nitrogen has 5 valence electrons so, it will form sigma bonds (sp3 hybrid orbitals) with each of the hydrogen atom. The remaining lone pair electrons will be situated above the atom. You ca look at this image I've pulled from Google.