[Avodah] Choice in mitzvot

[Rich, Joel via Avodah]

there are several mitzvot where HKB”H seems to give us different types of choice (marriage/divorce, Yibum/Chalitzah, Pidyon Haben/Give to Cohen, Pidyon Bcher Chamer/arifa) and also some prohibitions with a special fix (leftovers/burn). Anyone see anything written up (or have any thoughts) on why specifically these mitzvot?

Kol tuv 
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