Hello Sujatha.
Flat B would be a good choice. In Apartments pls do not consider the entry. because in none of the Vedic Epics, there is any reference of entries in tertiary vastu. The plot of the building is the primary vastu, The Bhavan (Building) is the secondary vastu.
In Flat be there is good enough opening in the NE and over all the Flat falls in the NE zone of the Building.
Regards.
Pavan Matkar
Wastu Wimarsh