Given Boolean Expression:
(P+Q'+R').(P+Q'+R).(P+Q+R')
we know that dual of a boolean expression is equivalent. Take dual of it:
PQ'R'+PQ'R+PQR'
Now simplify it.(I am taking dual because solving the given expression will be difficult hence, take dual and solve it)
=PQ'(R'+R)+PQR'
=PQ'+PQR'
=P(Q'+QR')
=P(Q'+R').
Now if we see option b) and take dual of it then we will be getting the above simplified expression.