Provide your best answer for the following question. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The question is: There are several different types of rock. Each type of rock is formed under different conditions. How are sedimentary rocks, such as shale and sandstone, formed?
Particles are compressed into layers.
Sedimentary rocks are formed from the accumulation and compaction of sediments.