This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gastrointestinal tract, Subject name: Pharmacology
Which one of the following is not an antacid? 
Select and explain. 
A. Magnesium sulfate, B. Magaldrate, C. Magnesium carbonate, D. Magnesium phosphate
A: Magnesium sulfate
Answer: A: Magnesium sulfate 
Explanation: Clasification of antacids 1.systemic( sodium carbonate,sodium citrate) 2.Non systemic(magaldrate,magnesium carbonate,magnesium phosphate,magnesium hydroxide,aluminium hydroxide,calcium carbonate) ESSENTIALS MEDICAL PHARMACOLOGY SIXTH EDITION KD TRIPATHI PG NO.626