‘Curled toe paralysis’ in chicks is a symptom caused due to the deficiency of

The correct option is Riboflavin.

Explanation:
Riboflavin, also known as Vitamin B₂, plays a crucial role in the health and development of chicks. A deficiency of riboflavin in their diet leads to a classic and distinct clinical symptom known as "curled toe paralysis".

How Deficiency Causes Curled Toe Paralysis:
Riboflavin is essential for the normal functioning of nerves, tissues, and energy metabolism as a precursor of coenzymes like flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). When chicks do not receive adequate riboflavin, it causes myelin degeneration in the peripheral nerves, particularly the sciatic nerve.
This sciatic nerve degeneration leads to neuromuscular dysfunction, causing the toes of the chicks to curl inward. Affected chicks walk on their hocks with their toes curled under, a characteristic condition that impairs their mobility and growth.