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

In Switzerland these glacial meltwaters are (1) ___________ for hydropower. In fact, water falling on 93% of Switzerland ultimately passes (2) I _____________ 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.