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: Pathology
Which of the following carcinoma most frequently metastasizes to brain? 
Select and explain. 
A. Small cell carcinoma lung, B. Prostate cancer, C. Rectal carcinoma, D. Endometrial cancer
A: Small cell carcinoma lung
Answer: A: Small cell carcinoma lung 
Explanation: . Small cell carcinoma lung