This is a test of commonsense with single/multi-choices. Complete the next sentence:

How to extract your dna
Create a mouth rinse.
To extract your dna from saliva, you'll need to create a mouth rinse first. You'll be mixing salt into water, because salt provides a rough, granular texture to help collect cells from your mouth.

Pick from:
[+] Soaking a piece of cardboard or newspaper in plain water first can make it easier to extract your dna. A basic mouth rinse will probably be sufficient; however, if you don't have time to soak an entire row of cell phones and other household objects, take a pinch of salt and use it instead.
[+] This process takes many months to complete, so it's important to have all this done before trying to extract your dna. Keep in mind that bacteria may be present in your mouth if you haven't already swallowed a certain amount of salt.
[+] For the process to work, add 1 teaspoon of regular sea salt to a gallon bucket. You don't need to be precise with your steps, since the salt is what draws out the trace minerals you want to remove from the dna and will eventually take juice from the antibodies responsible for your dna molecules.
[+] It also helps protect the negative phosphate ends of your dna, allowing it to precipitate out of the saliva. Mix one tablespoon of salt into 500 milliliters of clean drinking water.
The answer is:
It also helps protect the negative phosphate ends of your dna, allowing it to precipitate out of the saliva. Mix one tablespoon of salt into 500 milliliters of clean drinking water.