The correct option is B 745
Divide the given expression by 1000 and find the remainder to get the answer. (12345 × 54321) ÷ 1000 = (2469 × 54321) ÷ 200 → gives a remainder of (69 × 121) ÷ 200 = 8349 ÷ 200 → gives us a remainder of 149. Thus, the remainder would be 149 × 5 = 745. Hence, the last three digits would be 745.