Industrial melanism is an observation which supports evolution by:

The correct answer is Option (3) → natural selection

Option (3) natural selection — Correct. Before industrialisation white-winged moths were more common; after it, dark-winged moths became more common because they were hidden on soot-covered tree trunks. The better-suited form survived and left more offspring, so industrial melanism supports evolution by natural selection.

NCERT Extract:
What Are the Evidences for Evolution? – “… Another interesting observation supporting evolution by natural selection comes from England. In a collection of moths made in 1850s, i.e., before industrialisation set in, it was observed that there were more white-winged moths on trees than dark-winged or melanised moths. However, in the collection carried out from the same area, but after industrialisation, i.e., in 1920, there were more dark-winged moths in the same area, i.e., the proportion was reversed.”