Xiaoling summed up some of the chemistry knowledge she learned as follows. The group that made mistakes was a note in Experiment B of () Daily Life Experience.

A, gasoline can dissolve oil, so it can be washed, while PVC will produce hydrogen chloride gas when burning, which will produce irritating smell, and vinyl chloride will produce waxy smell when burning, so it can be distinguished, so A is right.

When you light the gas, you must ensure that it is pure. In impure gas, because it contains oxygen, it is easy to explode, but oxygen has no smell, so it is difficult to distinguish it by smell, so B is wrong.

C. molecules are composed of atoms. After the atom gains and loses electrons, the positive and negative charges are not equal and become ions. Atoms with the same number of protons are collectively called elements, so C is right.

D, industrial alcohol contains methanol, which is toxic. The main component of natural gas is methane, which is flammable and explosive when mixed with air. The main component of gas is carbon monoxide, which is also flammable. It may explode when mixed with air, so D is right.

So choose B.