One alternative - you can generate a truth table of the expression and see from the table what it is done, but I doubt that any Math teacher would like that, anyway
For example a
I believe that you can rearrange the terms and you can simplify them
e.g.
A'B XOR BC XOR AB XOR B'C'
becomes
A'B XOR AB XOR BC XOR B'C'
note:
A'B XOR AB - what does that tell you?
you can simplyfiy this to get just one variable
then take BC XOR B'C'
how can you get a more simple equivalent of this of a form Y XOR Z where Y and Z represent one variable e.g. B or C'.
When you have this done you should see the answer.
Example b is a tautology.