The above mentioned sentence would have ‘by, of’ as the correct answers for the blanks given.
Here,
By, is a preposition, which defines the source of service, by someone or something or the person who plans, makes, prepares or constructs a certain event or a thing.
With, is a preposition used for someone or something that accompanies the subject or also defines the help taken of an object or a person.
Of, is a preposition, which expresses, a relation between the subject and the lead object, so as to explain an event.
Therefore, Option B, ‘by, of’, would be the right combination, as the sentence speaks about Taj Mahal, and that it was built ‘by’, Emperor Shah Jahan in the memory ‘of’ (describing the relation, for which the event existed) Mumtaz Mahal.