Concept:A conjunction links two ideas by showing their relationship.Here, the second part gives the reason for the first part.Explanation:The sentence says business is poor, and then it tells us why."Workers are on strike" explains the cause of poor business.The word "because" is used to introduce a reason or cause.So the correct sentence is: "Business is poor these days because workers are on strike."The other options do not fit this cause-and-effect meaning.Answer:B. because