most means over 50% of something & ice caps and glaciers contain 69% of freshwater on earth ->  ice caps and glaciers contain most of the freshwater on earth  ice caps and glaciers contain most of the freshwater on earth & glaciers are a kind of major reservoir ->  glaciers are a major reservoir that contains most of the freshwater on earth  glaciers are a major reservoir that contains most of the freshwater on earth & ice sheet is a kind of glacier -> ice sheets are a major reservoir that contains most of the freshwater on earth