Subordinating conjunctions join two clauses. A clause is a group of words, which consists of a subject and a verb. For example take ‘I like the hotel’ and ‘It is expensive’. These two clauses have a subject and a verb. Subordinating conjunctions can show contrast or cause and effect. Some of the most common subordinating conjunctions that indicate contrast of ideas are: although, whereas, while… There are also coordinating conjunctions that combine two equal or similar parts. Most common ones are and, but, or... So the options A, C, D and E are examples for coordinating conjunctions, B is an example for subordinating conjunction. The correct answer is B.