单选题 It's natural for us to speculate about the reasons for their visit.
【正确答案】 B
【答案解析】[词义辨析] speculate与think同义，意为“思考，思索，推断，推测”。doubt “对……无把握，有怀疑”；work out“按某种方式发展，结果，解决”；reserve“保留，储备，保持”。