This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Embryology, Subject name: Anatomy
Blashcko lines represent - 
Select and explain. 
A. Invisible lines along which certain skin diseases develop, B. Lines along which villi of intestines are arranged, C. Arrangement of blood vessels in retina on fundoscopy, D. Lines along which migration of RBCs occur
A: Invisible lines along which certain skin diseases develop
Answer: A: Invisible lines along which certain skin diseases develop 
Explanation: Ans. is 'a' i.e., Invisible lines along which certain skin diseases develop Blaschko's lines* Blaschko's lines, also called the lines of Blaschko, named after Alfred Blaschko, are lines of normal cell development in the skin.* These lines are invisible under normal conditions.* They become apparent when some diseases of the skin or mucosa manifest themselves according to these patterns.* They follow a "V" shape over the back, "S" shaped whirls over the chest, and sides, and wavy shapes on the head.