Teacher:In this task, you are given a question and a context passage. You have to answer the question based on the given passage.
Teacher: Now, understand the problem? Solve this instance: what is the second type of energy source mentioned?, Context: In 2004, a large share of natural gas reserves in Iran were untapped. The addition of new hydroelectric stations and the streamlining of conventional coal and oil-fired stations increased installed capacity to 33,000 megawatts. Of that amount, about 75% was based on natural gas, 18% on oil, and 7% on hydroelectric power. In 2004, Iran opened its first wind-powered and geothermal plants, and the first solar thermal plant is to come online in 2009. Iran is the third country in the world to have developed GTL technology.
Student:
hydroelectric