In the following passage some of the words have been deleted. Read the passage carefully and select the correct answer for the given blank out of the four alternatives.

In Switzerland these glacial meltwaters are (1) __________ for hydropower. In fact, water falling on 93% of Switzerland ultimately passes (2) __________ at least one electric power plant before even (3) __________  the country. So one consequence is that melting glaciers help to (4) __________ for low rainfall in times of drought, filling reservoirs to supply the nation's (5) __________ supply.