Blashcko lines represent -

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.