At which stage in its life-cycle does the silkworm yield the fibre of commerce?

1. The question asks at which stage of the silkworm's life-cycle the silk fibre of commerce is obtained. 2. The silkworm larva spins a cocoon made of silk filament around itself before transforming into a pupa. 3. This cocoon, which encloses the pupa, is the source of commercial silk. 4. Harvesting typically occurs at the Pupa (C) stage, where the cocoon is collected before the adult moth (Imago) emerges and damages the continuous filament. The silk itself is produced by the Larva (B), but the harvestable product containing the fibre is the cocoon at the pupal stage.