The fossil fules are used as energy sources but they cause pollution and are what​

The correct answer is - non-renewable.

Explanation:

The non-renewable source of energy is the source of energy that can not be replaced naturally in the manner and the pace of the consumption of these sources. Nuclear, oil, fossil fuels, natural gases and other are an example of these type of energy source.

Fossil fuels were generated due to the decomposition of the dead plants and animals within the Earth over millions of years therefore these are called fossil fuels. These fuels are cause pollution by burning.

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.

chert is a sedimentary rock composed of microcrystalline or cryptocrystalline silica. with this little bit of information, you can come to the conclusion that your answer is c.  

explanation: