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 about carcinoids is not true  a) 80 % occur in appendix and ileum   b) Most of them metastatise to liver  c) 90 % of them cause carcinoma symptoms  d) They can occur in the lungs 
Select and explain. 
A. ac, B. bd, C. cd, D. acd
A: ac
Answer: A: ac 
Explanation: None