What is the name of department where has the largest number of professors with a Ph.D. degree?
return departments ;return professors of #1 ;return #2 that  have a Ph.D. degree ;return number of  #3 for each #1 ;return #1 where #4 is  highest ;return name of #5
['select', 'project', 'filter', 'group', 'superlative', 'project']