The answer is: Sancho is humbly asking for someone’s help, while Cugoano is asking for immediate and drastic changes in policies about slavery.
In Sancho's excerpt, he is glad if he can convince at least one person about the horrors of slavery and change his or her mind. On the other hand, Cugoano considers slavery should be abolished altogether.
The rest of the alternatives are incorrect because in the passage, according to Cugoano's book, he does not want a few people to be released but all slaves, while Sancho does mention God in his private letter.