Final answer:
The patient sitting at a 90-degree angle in bed would be most likely to develop a pressure ulcer from shearing forces due to the increased risk when the body slides in bed.
Step-by-step explanation:
The patient most likely to develop a pressure ulcer from shearing forces is b. Patient sitting at a 90-degree angle in bed. This position can cause shearing forces between the skin and underlying tissues when the body slides down in bed, increasing the risk for pressure ulcers. Shearing forces occur when layers of skin rub against one another or when skin remains stationary and the tissues below move, stretching and tearing the capillaries and blood vessels, and can be especially damaging over bony prominences. Preventative measures like regular repositioning and the use of special mattresses are vital to reducing the incidence of bedsores.