… caused the havoc, he sneaked off.

Analyze the question: The sentence is "....... caused the havoc, he sneaked off." We need a word that correctly begins the clause and links the two actions (causing havoc, then sneaking off).

Explain the concept: A perfect participle phrase ("Having + past participle") shows that one action was completed before another. For example, "Having finished his homework, he went out to play."

The subject "he" does both actions: he caused the havoc, and then he sneaked off. The perfect participle is a natural fit because the first action is finished before the second begins.

Test each option:

• A. On caused the havoc: "On" is a preposition and cannot be followed by the past tense "caused." Wrong. (It would need "On causing.")
• B. After caused the havoc: "After" can be followed by a clause, but "After caused" lacks a subject and uses the wrong verb form. It would need "After he caused" or "After causing." Wrong.
• C. Since caused the havoc: The same problem. There is no subject, and the meaning is wrong. Wrong.
• D. Having caused the havoc, he sneaked off: Correct. "Having caused" is a perfect participle phrase, and the sentence flows grammatically and logically.

Answer: The sentence reads: "Having caused the havoc, he sneaked off."

Exam tip: When a blank is followed by a past participle (caused, finished, done) and then a comma plus a subject, think of "Having + past participle". Also check that the word after the blank can actually follow the options. Prepositions like on, after and since need a noun, a gerund (-ing form), or a full clause with its own subject.