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
A 24-year old pregnant women developed a gingival infection that appears to be a bacterial origin. Which of the following drugs is safe to be used in this patient? 
Select and explain. 
A. Ampicillin, B. Clarithromycin, C. Sulfadiazine, D. Tetracycline
A: Ampicillin
Answer: A: Ampicillin 
Explanation: None