Answer : 3. "3439"
Explanation :

Answer: C) 3439 Explanation: The numbers 0,1,2,3,4,5,6,7,8,9 are 10 in number while preparing telephone numbers any number can be used any number of times.   This can be done in 105ways, but '0' is there   So, the numbers starting with '0' are to be excluded is 94 numbers.    Total 5 digit telephone numbers = 105- 94 = 3439