A kind of variable that a researcher purposely changes in an investigation is

If you get a map and put the countries a states all together it forms all one piece you can also tell because of the earth quakes

There are four nitrogenous bases that make up dna. the two pyramidines are thymine and cytosine. the two purines are adenine and guanine. these bases pair in a very specific way. adenine - thymineguanine - cytosine i remember it like this: a tall, good cat.