In the following passage, some words have been deleted. Select the most appropriate option to fill in each blank.

Comprehension:
In the generation of hydroelectric power, water is collected or (1) ______ at a higher elevation and led downward (2) ______ large pipes to a lower elevation; the difference in elevations is (3)
______ as the head. At the end of its passage down the pipes, the falling water (4) ______ turbines to rotate. The turbines in turn drive generators, (5) ______ convert the turbines’ mechanical energy into electricity.