The predicate in a where clause can involve boolean operations such as and. the result of true and unknown is___, false and unknown is ____, while unknow and unknown is______.
a) True and unknown is unknown, false and unknown is false, unknown and unknown is unknown.
b) True and unknown is true, false and unknown is false, unknown and unknown is unknown.
c) True and unknown is true, false and unknown is unknown, unknown and unknown is false.
d) True and unknown is true, false and unknown is unknown, unknown and unknown is unknown.