The correct answer is: C. concerted
A concerted effort is a joint action taken by a group of people or organizations towards a common goal. In this case, the principal and staff have made concerted efforts to enable the students to attend college on the days of the bus strike. This includes providing alternative transportation options, such as shuttle buses or carpooling, and offering flexible scheduling options, such as allowing students to make up missed work.
The other options are not as accurate. Option A, integrated, means combining or coordinating different parts into a whole. This does not accurately describe the efforts of the principal and staff, which are focused on a single goal. Option B, deliberate, means done with careful thought and planning. This is also not an accurate description, as the efforts of the principal and staff are not necessarily based on careful thought and planning. Option D, systematic, means done according to a plan or system. This is also not an accurate description, as the efforts of the principal and staff are not necessarily based on a plan or system.