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: Gynaecology & Obstetrics
The earliest indication of concealed acute bleeding in pregnancy is : 
Select and explain. 
A. Tachycardia, B. Oliguria, C. Postural hypotension, D. Low body temperature
A: Tachycardia
Answer: A: Tachycardia 
Explanation: Tachycardia