Maximum no of unsuccessful attempts, a thief can do in order to break a number locking system of 4 digits.
Select:  A) 9988  B) 9999  C) 9799  D) 9685  E) 6545
From 0 to 9999 there are 10000 four digit numbers   So maximum number of unsuccessful attempts = 10000 - 1= 
<gadget id="calculator">10000 - 1</gadget>
<output>9_999</output>
9999   ANSWER:9999
<result>B</result>
Maximum no of unsuccessful attempts, a thief can do in order to break a number locking system of 4 digits.