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: Microbiology
Cholangiocarcinoma is caused by -a) Fasciola infestationb) Clonorchis infestationc) Paragonimus infestationd) Ascaris infestatione) None of these 
Select and explain. 
A. ac, B. ab, C. ad, D. bc
B: ab
Answer: B: ab 
Explanation: Parasites

Schistosoma haematobium
Clonorchis sinensis
Opisthorchis viverrini

Malignancy

Squamous cell carcinoma of urinary bladder
Cholangiocarcinoma of liver, bile duct and Adenocarcinoma of pancreas
Cholangiocarcinoma of bile duct