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: Pharmacology
In antacid preparation aluminum hydroxide is added with magnesium salt because - 
Select and explain. 
A. Magnesium caused constipation, B. To counteracts constipating effect of aluminum hydroxide, C. To counteract the diarrhea action of aluminum, D. Aluminum salt causes diarrhea
B: To counteracts constipating effect of aluminum hydroxide
Answer: B: To counteracts constipating effect of aluminum hydroxide 
Explanation: Ans is 'b' i.e., To counteracts constipating effect of aluminum hydroxide o Magnesium salts are laxative and aluminium salts are constipating and the combination of both salts neutralises each other's action and bowel movement may be least affected.