Given a system with inputs a$,$b$,$c$,$d; which of the following boolean algebra equations could be a Canonical form representation of the system.

There is more than one answer so pick all that apply for credit.

ab $+$ ac $+$ bd

a'b'c'd' $+$ a'b'c'd $+$ a'b'cd'$+$ab'c'd'$+$ abc'd'

a'b'c'd' $+$ a'b'c'd $+$ a'b'cd'$+$a'bd

abc'd$+$ab'cd