a pure line is obtained through?

1. Mass selection
2. Clonal selection
3. Domestication
4. Inbreeding

The correct option is 1.

Pure line is a self pollinated descendent of a self pollinated plant. Desirable types already exist in population. Those are isolated through careful testing procedures. Another term used for this method of plant breeding is individual plant selection, as large numbers of plants are selected, but those are harvested individually, their individual progenies are grown and evaluated and then best progeny is released as a pureline variety.