Given the task definition and input, reply with output. This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.

181st Street is served by two New York City Subway lines; there is a 181st Street station at Fort Washington Avenue on the IND Eighth Avenue Line (A trains) and a 181st Street station at St. Nicholas Avenue on the IRT Broadway Seventh Avenue Line (1 trains). The stations are about 500 metres (550 yd) from each other and are not connected. The George Washington Bridge Bus Terminal is a couple of blocks south on Fort Washington Avenue. 181st Street is also the last south/west exit in New York on the Trans-Manhattan Expressway (I-95), just before crossing the George Washington Bridge to New Jersey.
How many subway lines serve 181st Street?