Concept: The blank needs a conjunction that gives a reason for the poor business.Explanation:The clause "workers are on strike" explains why business is poor."Because" is used to show cause or reason, so it fits correctly."so that" shows purpose, "whereas" shows contrast, and "no matter" shows concession, none of which fit here.Thus, the completed sentence is: "Business is poor these days because workers are on strike."Answer: A. because