Which was the main commodity produced by the Spanish in the Caribbean? gold sugar silver cotton

The main commodity produced by Spain (or any European country for that matter) would be sugar.  Sugar was a very valuable commodity in the colonial era--it was rare enough to be valuable in Europe.  Spices were still a luxury though sugar plantations would make sweets available to more people.  Sugar was also important in making rum, a staple on the world's sailing vessels.  Rum was often included as part of sailors' pay.  it allowed sugar to be preserved on long voyages.  Sugar was also important because its growth was part of the Triangle Trade which provided trade goods from Europe and slaves from Africa.  Per your other choices, gold and silver would be important to the Spanish, but only from North and South America.  The Spanish hoped to find gold in the Caribbean, but it was not there.  Cotton would be too labor intensive and would overly tax the Caribbean soil.