TASK DEFINITION: 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'.
PROBLEM: Sentence 1:In some situations , they have been accompanied , or followed , by civil unrest and armed rebellion . Sentence 2:nan

SOLUTION: SINGLE_VP_COORD

PROBLEM: Sentence 1:With Manuel 's death in 1180 the Byzantine empire was once again plunged into a succession crisis because his son Alexios II Komnenos was still a minor . Sentence 2:nan

SOLUTION: SINGLE_CONN_INNER_ANAPHORA

PROBLEM: Sentence 1:Leaching powdered 96 -- 97 % pure silicon with water results in ~ 98.5 % pure silicon , which is used in the chemical industry . Sentence 2:However , even greater purity is needed for semiconductor applications , and this is produced from the reduction of tetrachlorosilane or trichlorosilane .

SOLUTION:
PAIR_CONN