题目选项分析

To help preserve ancient Egyptian monuments threatened by high water tables, a Swedish engineering firm has proposed installing pumps, perhaps solar powered, to lower the underground water level and digging trenches around the bases of the stone walls.

To help preserve ancient Egyptian monuments threatened by high water tables, a Swedish engineering firm has proposed installing pumps, perhaps solar powered, that lower the underground water level and that trenches be dug around the bases of the stone walls.