In his study of Senegambian cleric Shaykh Mass Kah (1827-1936), Bala S. K. Saho notes that it is difficult to fully (i)____________ many of the oral accounts on which the study relies. Saho's work shows, however, that despite this absence of (ii)____________, oral history can provide useful sources from which historians can reconstruct the past. A. comprehend B. partiality C. reproduce D. argumentation E. validate F. corroboration