This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Basics of Psychiatry, Subject name: Psychiatry
[{'content': 'Which of the following is the test for immediate memory? \nSelect and explain. \nA. Serial (100-7) subtraction test up to 4 steps, B. Digit span forward upto 5 digits with 2 skips allowed, C. Digit span backwards up to 5 digits with 2 skips allowed, D. Serial (20-1) subtraction test up to 5 steps', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Immediate memory test (1) Digit span test - two types-digital forward test and digital backwards test - Forward up to 5 digits is considered normal . - Backward up to 4 digits is considered normal. (2) Serial 7 subtraction test - subtract 7 from 100 up to 5 steps', 'role': 'assistant'}]