Which phrase defines “immutable” best?
not desirable
not comparable
not changeable
not edible

The phrase that best defines “immutable” is not changeable, which is by dictionary definition, ‘unable to be changed’. The above choices do not answer to the needed word to the question. Not changeable can be applied to anything, a chemical, place, memory, doctrine, law, etc. Laws for examples are based upon nature and not changeable, therefore we could say that: Nature’s laws are immutable by men. Memories are immutable because one cannot change what happen in the past, however he could change it and distort it according to his perspective.