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: Psychiatry
Serial 7 substraction is used to test ? 
Select and explain. 
A. Working memory, B. Long term memory, C. Mathematical ability, D. Recall power
A: Working memory
Answer: A: Working memory 
Explanation: Ans. A. Working memorySerial sevens substraction testSerial sevens, counting down from one hundred by sevens, is a clinical test used to test mental function; for example, to help assess mental status after possible head injury or in suspected cases of dementia.This well-known test, in active documented use since at least l944,was adopted as pa of the mini-mental state examination.The test is also used in determining when a patient is becoming unconscious under anaesthetic, for example prior to major dental surgery.