This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Other topics and Adverse effects, Subject name: Pharmacology
Which of the following drug is an Immunostimulant? 
Select and explain. 
A. Prednisolone, B. Levamisol, C. Cyclosporine, D. Thalidomide
B: Levamisol
Answer: B: Levamisol 
Explanation: (Ref: Goodman & Gliman 11/e p1422) All other drugs listed in the options posses immunosuppressant propeies.