For valleys and other wider channels – especially in East Asia and South America, where examples can still be found – ropes made of various grasses and vines tied together were hung in suspension for single-file crossing. Materials were (i)____________, and there were (ii)____________, since the work was done by slaves, soldiers, or natives who used the bridges in daily life. A. scarce and meager B. few labour costs C. free and abundant D. more demanding requirements E. expensive and widespread F. myriad numinous forces