sentences:  The biplane C-1s were evolved from the Douglas World Cruiser design, with the pilots side-by-side in an open cockpit forward of the wing.Two tanks were installed in their cargo compartments, attached to a lead-weighted length of fire hose.The nozzle of the hose had a quick-closing valve on the tanker's end and was tightly wrapped with copper wire, one end of which could be attached to a corresponding copper plate mounted in "Question Mark" to ground the hose.