Concept: The question tests on the basics of Counting/Combinations
Solution:
From (i) a can be either 4 or 5. So it can be filled in 2 ways.
From (ii) d can be either 0 or 5. So it can be filled in 2 ways.
From (iii) b and c can take on values of 3, 4, 5 and 6, with b < c.
So b can take any 4 values and c can take any 3 values. The total numbers = 4 * 3 = 12. These include numbers where b > c and hence we need to take half of 12 which is 6. (34, 35, 36, 45, 46 and 56)
Total such numbers = 2 * 6 * 2 = 24
Option C