life·blood /ˈlaɪfˈblʌd, ˌblʌd/
  鮮血,血,生機的根源
  Life·blood n.
  1. The blood necessary to life; vital blood.
  2. Fig.: That which gives strength and energy.
     Money [is] the lifeblood of the nation.   --Swift.
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  lifeblood
       n 1: the blood considered as the seat of vitality
       2: an essential or life-giving force; "water is the lifeblood
          of India"