把先行词放在从句中去如需要在先行词前加上介词,就说明作状语.在这句中变为physical strength was all you needed to make a living (in the days)
要看不定式有几个,如一个谓语用单数.这题正是这样.
对比下面 when to build the hotel and where to find construction are being discussed.
when and where to build the hotel is being discussed.