I think the answer would b C
Answer: PCl₃O
Explanation:
1) The chemical formula tells the composition of a compound in terms of the ratio of number of atoms of each element that consitutes such compound.
2) You use the chemical symbol for each kind of atom (element) and subscripts to the right of each symbol to tell the number of atoms of each element.
3) For example, O₂ means two atoms of oxygen. Al₂O₃ means two atoms of aluminum and 3 atoms of oxygen.
4) Therefore, PCl₃O means a ratio 1 : 3 : 1 for phosphorus, chlorine, and oxygen.
Hence, PCl₃O is the chemical formula of your compound.
Density is too do with how much of a mass is condensed or concentrated in a unit of volume: Density = Mass / Volume
So applying it to the given data:
10/2 = 5
Density is 5 g/ml
[ml is usually the equivalent of one cm³, so it could also be written as 5 g/cm³ I guess]