Haemophilia is a genetic disorder that affects the blood's ability to clot normally. It is caused by a deficiency in one of the clotting factors in the blood, specifically factors VIII or IX. As a result, people with haemophilia can experience severe bleeding episodes even from minor injuries.

The correct answer to the question is B) Colour blindness. Colour blindness is a condition in which a person is unable to distinguish between certain colours. It is also a genetic disorder caused by a mutation on the X chromosome. Haemophilia is also caused by a mutation on the X chromosome, which means that it is more commonly found in males than in females.

The link between haemophilia and colour blindness is due to the fact that both disorders are X-linked recessive genetic disorders. This means that the gene mutation responsible for the disorder is located on the X chromosome, and the disorder is only expressed when a person inherits two copies of the mutated gene (one from each parent).

Since haemophilia and colour blindness are both X-linked recessive disorders, they are often passed down from a mother who carries the mutated gene on one of her X chromosomes to her son. Females are less likely to be affected by haemophilia or colour blindness because they have two X chromosomes, and would need to inherit two copies of the mutated gene to be affected. However, females can still be carriers of the disorder and pass it down to their children.