what is the 2nd biggest mountain in africa?
return africa ;return mountains in  #1 ;return size of #2 ;return #2 where  #3 is the  highest ;return #2 besides  #4 ;return size of #5 ;return #5 where  #6 is the  highest
['select', 'project', 'project', 'comparative', 'discard', 'project', 'comparative']