Answer:
Most of the electricity in America is made from fossil fuels.
Explanation:
The sentence which belongs in a summary of the text is that "Most of the electricity in America is made from fossil fuels".
If one is to give a summary of the given passage, it will be seen that most of the electricity used in America is usually made from fossil fuels. In fact, this seem to be the message that the passage is trying to convey.
It revealed that coal was the primary source for generating electrical power in America and this same coal is a fossil fuel.
