Ans. is 'd' i.e., Abrasion o Abrasion is a superficial injury involving superficial layer of epidermis and is caused by hard, blunt and rough object due to friction between skin and the object. Scab or crust is formed over exposed raw surface and most injuries heal without scar as they are superficial.o Age of abrasion can be calculated by following changes:-# Fresh:Reddish# 12-24 hours:Scab forms, which is red in colour# 2-3 days:Reddish brown Scab# 4-7 days:Abrasion starts healing (epithelization) from periphery# 7-10 days:Scab dries up and falls off# 10-12 days:Healing is complete (skin colour returns to normal)o Type of abrasion are:-1) Scratches (linear abrasion):# It is an abrasion with legnth but no significant width produced by a sharp object e.g., pin, needles, knife, thorn and nail etc.# Point scratch is a very superficial incision produced by a sharp or pointed object not sharp enough to incise but pointed enough to produce scratch.2) Grazes (Sliding abrasion/scraping abrasion/grinding abrasion):# It is the most common type of abrasion, produced when a broad surface of skin slides against rough surface, e.g., during vehicular accidents. Injury is due to friction. The surface of injury show irregular parallel lines, i.e., furrows or grooves.# A violent lateral graze, due to rubbing of skin (as in dragging) is known as brush burn (Gravel rash).# Friction burn (Scuff or brush abrasion) occur due to tangential contact with a smooth surface or when the skin is covered by clothing. It is an extensive superficial, reddened excoriated area without bleeding and with little or no linear mark.3) Pressure abrasions (crushing or friction abrasions) :# Though it is called friction abrasion, it results from pressure of the object on the body with no or little friction (it is a misnomer).# It is caused by crushing of superficial epidermis due to inward directed movement of object at around 90deg to skin.# Example are ligature marks in hanging/strangulation, teeth bites and nail marks.4) Impact abrasion (Imprint or contact abrasion):# It is caused by impact (but not pressure) with a rough object, when the force is applied at or near 90deg to skin surface.# It is depressed below surface unless associated with contusion (bruise).