Final answer:
The Dutch established themselves as an economic powerhouse in the Caribbean through legitimate trade, piracy, and smuggling. All these practices contributed to their economic expansion in the region.
Step-by-step explanation:
When the Dutch were establishing themselves as an economic powerhouse in the Caribbean, they engaged in a variety of practices. Historical records show that they indeed practiced legitimate trade, but they also engaged in piracy and smuggling. The economic activities of the Dutch during this period in the Caribbean were complex and varied, which often included pursuing all available means to enhance their economic influence. Hence, the correct answer to the question is d. all of the above.