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: Biochemistry
All are bad cholesterol except: 
Select and explain. 
A. HDL, B. LDL, C. VLDL, D. IDL
A: HDL
Answer: A: HDL 
Explanation: HDL can remove cholesterol from atheroma within aeries and transpo it back to the liver for excretion or re-utilization, which is the main reason why HDL-bound cholesterol is sometimes called "good cholesterol", or HDL-C. A high level of HDL-C seems to protect against cardiovascular diseases, and low HDL cholesterol levels (less than 40 mg/ dL or about 1mmol/L) increase the risk for hea disease. Cholesterol contained in HDL paicles is considered beneficial for the cardiovascular health, in contrast to "bad" LDL cholesterol.