Explanation
A number greater than 1000 must have at least 4 digits. Using the given digits {0,1,2,3} without repetition, we can only form 4-digit numbers.
For a 4-digit number to be valid, the first digit (thousands place) cannot be 0.
Thousands place: Can be filled by any of the 3 non-zero digits {1,2,3}.
Hundreds place: Can be filled by any of the remaining 3 digits (including 0, since one digit has been used in the thousands place).
Tens place: Can be filled by any of the remaining 2 digits.
Units place: Can be filled by the remaining 1 digit.
Total numbers =3×3×2×1=18
All these 18 numbers are 4-digit numbers and are definitely greater than 1000.
Conclusion: There are 18 such numbers.
Correct Option: (b) 18
