Final answer:
The sentence requires the name of a venture that Sira and Candelaria plan to open with their money, which could be a business, store, or restaurant, depending on the context.
Step-by-step explanation:
The blank in the sentence 'Sira and Candelaria are going to open _________ with the money they received for the pistols.' needs to be filled with the type of venture or establishment they plan to open. Without specific context, one could assume Sira and Candelaria might open a business, such as a store, restaurant, or another type of commercial enterprise. The choice depends on further context within the story or lesson from which this sentence is taken.