Mr Sewall was referring to a biblical scenario, The one of Joseph, to talk about how slavery should not be considered whatsoever.
"And let every other power know that this Hemisphere intends to remain the master of its own house". This passage from Kennedy's inaugural address is a metaphor.
'a' is correct, As 'valuable ' is a polysyllable word,' the most' has to be used to form the Superlative degree
