Which of these is a disadvantage of using natural gas A It is not considered safe to use in homes. B Scientists have developed new ways of extracting it C It burns less cleanly than other fossil fuels D Extraction through fracking can contaminate groundwater

A

Explanation:

Natural gas is flammable. A natural gas leak in a house can cause potential fires, and inhaling the gas can cause natural gas poisoning.

* Answer B: The fact that scientists have developed new ways of extracting natural gas - is an advantage, not a disadvantage.

* Answer C is wrong, because compared with some other fossil fuels, natural gas emits the least amount of carbon dioxide into the air when combusted -- making natural gas the cleanest burning fossil fuel of all.

* Answer D: the content of the statement is about the production process, not about using of natural gas.

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1. a)c-14 has two more protons

2. d)they have different numbers of protons, neutrons, and valence electrons; they are all gases at room temperature.

3. c) iron and nickel.