In this task, you are given two sentences in the English language and your task is to classify them into one of their discourse types. A discourse type is an indicator to classify the given two sentences on the basis of a co-text as well as a relevant context. There are 13 discourse types in total which are 'SINGLE_S_COORD', 'SINGLE_CATAPHORA', 'SINGLE_CONN_INNER', 'SINGLE_APPOSITION', 'SINGLE_VP_COORD', 'SINGLE_CONN_START', 'PAIR_ANAPHORA', 'PAIR_CONN', 'SINGLE_RELATIVE', 'SINGLE_CONN_INNER_ANAPHORA', 'SINGLE_S_COORD_ANAPHORA', 'PAIR_CONN_ANAPHORA' and 'PAIR_NONE'.
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Question: Sentence 1:The fluid pumping efficiency of a valveless system , however , is not necessarily lower than that having valves . Sentence 2:In fact , many fluid - dynamical systems in nature and engineering more or less rely upon valveless pumping to transport the working fluids therein .

Answer: PAIR_CONN


Question: Sentence 1:Seeking the power of the Flash so that he can restore history according to his own vision rather than another , Sinestro cuts off Abin 's hand , severing his connection with his ring . Sentence 2:nan

Answer: SINGLE_CATAPHORA


Question: Sentence 1:The format has grown to many other cities , including New York , Los Angeles , Denver , Miami , and Albuquerque , NM . Sentence 2:But more Recently , the format has been replaced in several cities .

Answer:
PAIR_CONN