DNA<span> is a double helix, while RNA is a single helix. Both have sets of nucleotides that contain genetic information. </span>DNA<span> is a molecule that contains the instructions an organism needs to develop, live and reproduce.</span>
On May 14, 1796, Jenner<span> took fluid from a cowpox blister and scratched it into the skin of James Phipps, an eight-year-old boy. A single blister rose up on the spot, but James soon recovered. On July 1, </span>Jenner<span> inoculated the boy again, this time with smallpox matter, and no disease developed. The </span>vaccine<span> was a success.</span>
The correct answer is: Layer 1, layer 2, and layer 4 in all three regions.
The index fossils are fossils that are commonly used for identifying a geological period of time, and these fossils are also very wide spread, as well as having a rapid evolutionary trends.
By this picture, we can easily see that even though we have rock strata from different regions, the same layers contain the same fossil, and it is a fossil that also is rapidly evolving so has a minor change in each layer.
An independent variable is a variable which change is not affected by that of another variable. By process of elimination you can take out B and C. An independent variable can also change so that takes out A. That leaves D.
