Which one of the following is the correct sequence in respect of the Roman numerals—C, D, L and M?

The Roman numeral symbols and their standard values are: L = 50, C = 100, D = 500 and M = 1,000, as listed in standard references on Roman numerals. Ordering these by numerical magnitude from largest to smallest gives M (1,000) > D (500) > C (100) > L (50). Therefore the sequence M > D > C > L corresponds to option 3. The choice follows directly from comparing the numeric values assigned to each Roman letter and arranging them in descending order of value.