Option 1 suggests that smelting units, pens and pencils, and paints are sources of lead poisoning. While smelting units and paints can indeed be sources of lead, pencils no longer use lead.
Option 2, the correct answer, proposes that smelting units and paints are sources of lead poisoning. This is accurate because both contain lead; smelting units as a part of their processing of metals and many paints, particularly older ones, include lead components.
Option 3 suggests that pens and pencils, and hair oils and cosmetics are sources of lead poisoning. This is incorrect because neither of these is typically a source of lead.
Option 4 claims that all four options are sources of lead poisoning, but as previously discussed, pencils and cosmetics typically don`t contain lead and hence, can`t be sources of lead poisoning.