Doctor: There will be more local cases of flu infection this year than there were last year. In addition to the strains of flu that were present in this area last year, a new strain has infected some people this year. The conclusion of the doctor's argument can be properly drawn if which one of the following is assumed? ['It is rare for new strains of flu to appear.', 'The new strain of flu cannot be addressed with the approaches used to deal with the strains of flu that were present last year.', 'There will be no decline this year in the number of cases of flu infection due to strains that were present last year.', 'The new strain of flu is expected to be more dangerous than the strains of flu that were present last year.']