Cyanosis is the appearance of blue or purple coloration of the skin or mucous membranes due to low oxygen saturation.

• A. Decompose
• B. Decomposition
• C. Cartridge (firearms)
• D. Cyanosis

Answer: (D)

Cyanosis is the color change described: blue or purple tint of the skin and mucous membranes caused by low oxygen saturation in the blood. It happens when there’s more deoxygenated hemoglobin circulating, making tissues look bluish, especially in exposed areas like lips and nail beds. The other options don’t fit this phenomenon—decompose and decomposition refer to breaking something down, while cartridge relates to firearms. So the term that matches this description is cyanosis.