Fact 1: Coal is used to produce electricity by burning in coal-fire power stations. Fact 2: Solid refined coal is easy to transport and can be used in coal-burning equipment. Given the two facts above, solid materials used to produce electricity by burning in what need to be transported firs?

Choose your answer from: 1). Conifers 2). animals 3). it needs them 4). humans 5). heat energy 6). important habitats 7). power stations 8). batteries
The answer is:
7).