The correct option for the sentence "Government should prevent smugglers .... their contraband" is C. from selling. Let's break down why this is the best choice and why the other options are less suitable. Step-by-Step Explanation

1. Understanding the Sentence Structure:
2. The sentence is structured to indicate that the government has a role in stopping smugglers from doing something illegal with their contraband. The verb "prevent" is key here, as it indicates an action that stops someone from performing another action.
3. Identifying the Correct Preposition:
4. The verb "prevent" is typically followed by the preposition "from" when indicating what action is being stopped. This is a common grammatical structure in English. For example, we say "prevent someone from doing something."
5. Analyzing Option C:
6. C. from selling: This option correctly uses the preposition "from" followed by the gerund "selling." The phrase "prevent smugglers from selling their contraband" clearly communicates that the government should take action to stop smugglers from engaging in the act of selling illegal goods.
7. Examining the Other Options:
8. A. to sell: This option suggests that the government should prevent smugglers with the intention of selling their contraband. However, this construction does not fit well with the verb "prevent," which requires a focus on stopping an action rather than indicating intention.
9. B. to be selling: This option implies an ongoing action but is awkward in this context. It suggests that the government should prevent smugglers who are in the process of selling, but it does not convey the intended meaning as clearly as option C.
10. D. having sold: This option refers to a completed action, suggesting that the government should prevent smugglers after they have already sold their contraband. This does not align with the proactive nature of the government's role in preventing illegal activities.

Summary of Key Points

• The correct answer is C. from selling because it uses the appropriate structure with "prevent" and the gerund form.
• The other options either misplace the focus of the action or do not fit grammatically with the verb "prevent."
• Understanding the relationship between verbs and their required prepositions is crucial for constructing grammatically correct sentences.

Revision Summary

• The correct answer is C. from selling.
• "Prevent" is followed by "from" + gerund (verb + -ing).
• Other options do not fit the grammatical structure or intended meaning.
• Always check the verb-preposition combinations in English for clarity and correctness.