In this task, you are given a paragraph, and your job is to generate comma-separated entities present in the given paragraph. Generate entities from a given passage in such a way that (i) they are present in the paragraph, (ii) they are non-duplicate, (iii) they underwent a state change during the process. Avoid creating entities that (i) aren't present in the process paragraph and (ii) aren't significant. 

[Q]: Choose what you want to write your letter on. Think of what you want to say. Write some nice things!. Place the letter into an envelope. Put a stamp on the top right corner of the face of the envelope. Write the address of the recipient on the envelope. Put the envelope in your mailbox. Raise the flag on your mailbox, indicating to the mailman that you have outgoing mail. 
[A]: envelope ,flag on your mailbox ,letter ,nice things ,stamp 


[Q]: Rock begins as magma from a volcano. The magma cools. Crystals form and the magma become igneous rocks. The igneous rocks break down into sediment. Become sedimentary rocks. If subjected to heat and/or pressure from plate-tectonic activity the sedimentary rocks become metamorphic rock. The metamorphic rocks melt. Become magma again. 
[A]: magma ,crystals ,igneous rocks ,sediment ,sedimentary rocks ,metamorphic rocks ,rock 


[Q]: MRNA is made during the first step of protein synthesis, which is transcription. The DNA's genetic information, or secret code, gets written onto a strand of mRNA. Transcription takes place in the nucleus. The next step in making a protein is called translation. The mRNA attaches itself to the ribosome.  Read more at: http://www.ducksters.com/science/biology/proteins_and_amino_acids.php This text is Copyright    Ducksters. Do not use without permission. The ribosome figures out where to start on the mRNA by finding a special three letter "begin" sequence called a codon. The ribosome then moves down the strand of mRNA. When the ribosome sees the "stop" code, it ends the translation and the protein is complete. 
[A]:
MRNA ,DNA's genetic information ,protein ,mRNA ,ribosome