Which of the non-living things listed below, were once part of a living thing?

Butter, Leather, Soil, Wool, Electric bulb, Cooking oil, Salt, Apple, Rubber

(1) Butter : Butter is non-living, but it is made by milk and the cow gives milk and the cow is living the organism.

(2) Leather : Leather is non-living but it is obtained from the skin of animals and animals are living organisms.

(3) Wool : Wool is obtained from the sheep and sheep is a living organism.

(4) Cocking oil : Cooking oil is obtained from plants.

(5) Apple : Apple is obtained from tree.

(6) Rubber : Rubber is obtained from plants.

So required answer is Butter, Leather, Wool, Cocking oil, Apple, Rubber.