Concept:
This question tests the knowledge of double consonants and vowel placement in multi-syllabic academic English words. Words of Latin origin often maintain specific consonant pairings (like 'cc', 'ss', or 'ssi').
Step 1: Verification of Options (A), (B), and (C).
• Garrulous: Spelled correctly. Note the double 'r'. It means excessively talkative, especially on trivial matters.
• Inundate: Spelled correctly. It means to overwhelm (someone) with things or people to be dealt with; to flood.
• Surreptitious: Spelled correctly. Note the double 'r' and double 'p'. It means kept secret, especially because it would not be approved of.
Step 2: Detection of spelling flaw in Option (D).
The word given is "vicisitude".
The correct spelling is "vicissitude".
The error is the omission of the second 's'. In English, the word for a change of circumstances or fortune (typically one that is unwelcome) requires a double 's' after the first 'i'.