Different kinds of sedimentary rocks exist because

A. they were formed in different places
B. their formation took different lengths of time
C. they were formed by sediments from different rocks
D. they have been cut differently

I THINK ITS C is that right?

Right.

Can you explain it?

http://geology.com/rocks/sedimentary-rocks.shtml

What uses wind to generate electricity?

windmills

Which source is not a source for fossil fuels?

coal mine
ancient swamps
ancient living organisms
corn fields

And your answer is?

corn fields?

I think its corn fields but im not sure

You're right. Cornfields are not sources of fossil fuels. The products do not involve any fossils.

What are they asking in this question?

Which is an alternative source of
energy?

The main sources of our energy for heat, electricity, and vehicles) are those made of fossils. These are finite sources and will run out some day. They also produce pollution.

Alternate sources of energy are those that are not made of fossils. Some examples are wind and solar power.

http://www1.eere.energy.gov/kids/renergy.html

C they were formed by different sediment rocks