"We know his reasons."
Translation:Sabemos sus motivos.
ugh, too bad it doesn't accept razones, though true, perhaps motivos would be better, but it's almost a trick question because for an english speaker seeing the word "reason" the first word that is going to come to mind is "razon"
Both sabemos and conocemos work (I've tested). Would love a small unit devoted to helping us understand the differences between those two words.