The word 'although' introduces a subordinate clause that presents a contrasting or unexpected idea compared to the main clause. This highlights a concession or a contrast. Therefore, the correct answer is B. * **Core concept**: Understanding the function of 'although' as a subordinating conjunction indicating contrast. * **Solution analysis**: 'Although' signals that the information in the two clauses is in opposition to each other, making option B the only logically consistent choice. * **Option A Analysis**: Incorrect because 'although' shows a contrast rather than similarity. * **Option C Analysis**: Incorrect because 'although' does not show a cause and effect relationship. * **Option D Analysis**: Incorrect because 'although' does not add extra detail but provides an opposite statement. * **Easy mistake**: Confusion between 'although' and conjunctions like 'and' or 'because'.