Which of the following material is bio-degradable ?

Biodegradable materials are substances that can be broken down into simpler, non-toxic components by the action of microorganisms like bacteria and fungi. Wool is a natural fiber obtained from animals (such as sheep) and is primarily composed of the protein keratin. Because it is an organic material, it can be decomposed by biological processes within a relatively short period.

On the other hand, plastic cups are synthetic polymers that can take hundreds of years to degrade. Glass bottles are made of inorganic silica and do not decompose biologically. Aluminium foil is a metal; while it can be recycled or may eventually corrode, it is not broken down by biological organisms. Thus, wool is the only biodegradable material among the given options.