Commercial silk is obtained from

Silk is a type of natural protein fibre that may be woven into clothing. 

Fibroin makes up the majority of the protein fibre that makes up silk, which is secreted by certain insect larvae to create cocoons. 

A cocoon is a space where a pupil develops into an adult.

Commercial silk is made from raised silkworm pupae, which are bred to create a white, mineral-free silk thread. 

Before the adult moths emerge, the pupae are either dipped in hot water to destroy them or pierced with a needle.

Hence, option A is the correct answer.