Question

what is a hydroelectric power plant?
a turbine that is place in a river and turned by it.
a dam that is built across a river, making a body of water that can be used to create energy.
a chemical reaction caused by sending a very strong electric pulse through a river.

Explanation:

A hydroelectric power plant involves building a dam across a river. This dam creates a reservoir (a body of water). The stored water's potential energy is converted to kinetic energy as it flows through turbines. The turbines are connected to generators which produce electricity. The first option only mentions a turbine (a part of the plant, not the whole plant). The third option is incorrect as it's about a chemical reaction (not related to hydro - electric power generation principles).

Answer:

A dam that is built across a river, making a body of water that can be used to create energy.