Failure to act within said period shall be deemed to be a grant of tentative approval of the development plan as submitted. In the event, however, that tentative approval is granted subject to conditions, the landowner may, within 30 days after receipt of the official written communication of the Board of Supervisors, notify the Board of Supervisors of his refusal to accept all said conditions, in which case, the Board of Supervisors shall be deemed to have denied tentative approval of the development plan. In the event that the landowner does not, within said period, notify the Board of Supervisors of his refusal to accept all said conditions, tentative approval of the development plan, with all said conditions, shall stand as granted.