'Y' is a man-made fibre obtained from a natural source. What could be 'Y'?

Rayon is a man-made (semi-synthetic) fibre derived from cellulose, a natural source (wood pulp). It is also known as 'artificial silk'. Nylon and acrylic are fully synthetic fibres made from petrochemicals, not natural sources. Jute is a natural fibre, not man-made. Hence rayon is the correct answer as a manufactured fibre from a natural source.