This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
Which of the following is true of psoriatic arthritis- 
Select and explain. 
A. Involves distal joints of hand and foot, B. Pencil in cup deformity, C. Sacroilitis, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: None