sakali nails it:

sakali wrote:The correct idiom usage:
Descend FROM
The great bankers never descend from their tower to deal with people like you and me

and

Descendant OF
Rebecca Smith, a descendant of the Austen family, said she was very pleased with the exhibition

this is correct.

as for "may" vs "might", one rule often followed is that "might" is used for sentences that are otherwise formulated in the past, and "may" is used for sentences that are otherwise formulated in the present/future. this is a lot like the rules for "can" vs. "could".

however, i don't recall seeing an official problem that explicitly tests may vs. might (as opposed to will/would and can/could, both of which i've seen tested).
even on this problem, the distinction is not strictly dispositive: the problem can be resolved by the above idiomatic usage split instead.

to the posters on this site: have any of you ever seen an OFFICIAL problem that tests may vs. might? (especially if that distinction is actually required to solve the problem)