Performing frequent and thorough skin assessments is essential for identifying early signs of pressure ulcers and implementing appropriate preventive measures in patients with limited mobility.

Incorrect choices:

b. Applying petroleum jelly to vulnerable areas may create a barrier but does not address the underlying issue of pressure and does not substitute for regular skin assessments and preventive measures. 

c. Placing the patient on an air mattress can provide pressure redistribution, but it should be used based on individualized assessment and healthcare provider recommendations. Skin assessments remain essential. 

d. Encouraging the patient to sit for prolonged periods increases the risk of pressure ulcers. Adequate repositioning and regular mobilization should be prioritized to prevent skin breakdown.