4. A
because PbCl2 is an ionic compound and it's solid, so it's a substance.
It cannot be mixture, because it's a pure molecule.
5. D
despite that both substances are gases, colorless they are different molecules, so they should have different either chemical and physical properties
6. C
this substance made from W atoms and others are made from molecules
The answer is the 3rd one
Cirrhosis is liver damage that can lead to scarring and even liver failure.
Hepatitis b and c are caused by a virus, and alcoholic hepatitis is caused by drinking too much alcohol.
