Arrange the given words in the sequence in which they occur in the dictionary.
Radiant

Racial

Raider

Ramble

Radical

To arrange the words in alphabetical order:
All words start with Ra-.

Compare the 3rd letters:

Racial (3rd letter 'c')

Radiant (3rd letter 'd')

Radical (3rd letter 'd')

Raider (3rd letter 'i')

Ramble (3rd letter 'm')

Clearly, Racial (2) comes first.

Next, compare Radiant and Radical up to their 5th letters:

Radiant (5th letter 'n')

Radical (5th letter 'a') -> Radical (5) comes before Radiant (1).

Next in sequence is Raider (3), followed by Ramble (4).

Putting it all together, the exact dictionary order is:
2. Racial → 5. Radical → 1. Radiant → 3. Raider → 4. Ramble

Therefore, the sequence is 2, 5, 1, 3, 4 (which matches option C structurally).