Explanation:

ATM stands for Automated Teller Machine. Its primary and most recognized function is to facilitate financial transactions, most notably the 'Withdrawal of cash without staff'. Option (c) accurately describes this core service. Option (a) 'Branch of bank' is a physical location, not an ATM. Option (b) 'Staff counter of bank' refers to a human-operated service point. Option (d) 'All of these' is incorrect as (a) and (b) are not definitions of an ATM. Option (e) 'None of these' is incorrect because (c) is the correct description of an ATM's main purpose.