This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Biostatistics, Subject name: Social & Preventive Medicine
about test of significance between two large population, one of the following statements is true- 
Select and explain. 
A. Null hypothesis states that 2 means are equal, B. Standard error of difference is the sum of the standard error of 2 means, C. Standard error of means are equal, D. Standard error of difference between populations calculated
D: Standard error of difference between populations calculated
Answer: D: Standard error of difference between populations calculated 
Explanation: .