Mall owner: Our mall's occupancy rate is so low that we are barely making a profit. We cannot raise rents because of an unacceptably high risk of losing established tenants. On the other hand, a mall that is fully occupied costs about as much to run as one in which a rental space here and a rental space there stands empty. Clearly, therefore, to increase profits we must sign up new tenants.Which of the following, if true, most seriously weakens the argument?
【选项】The mall's occupancy rate, though relatively low, has been relatively stable for several years.