Use the Following Information When Answering the Corresponding Questions)

Use the following information when answering the corresponding questions) .
A study by Krings et al. investigated Neanderthal DNA by amplifying 30 000- year- old samples and sequencing it. M. Krings Stone, R.W. Schmitz, H. Krainitzki, M. Stoneking, and S. Pääbo. 1997. Neandertal DNA sequences and the origin of modern humans. Cell 90:19- 30) .
Here is part of the lead paragraph in the "Methods" section of the Krings et al. paper:
Protective clothing was worn throughout the sampling procedure. Instruments used were treated with 1 M HCl followed by e rinsing in distilled water. After removal, the sample was immediately put into a sterile tube for transport to Munich. All subse manipulations of the sample, and experimental procedures prior to cycling of PCR reactions, were carried out in laboratories dedicated to the analysis of archaeological specimens, where protective clothing, separate equipment and reagents, UV irradia other measures to...
A concluding paragraph of the Krings et al. paper states:
It must be emphasized that the above conclusions are based on a single individual sequence; the retrieval and analysis of mtD sequences from additional Neanderthal specimens is obviously desirable. If this proves possible, then the potential exists to address several questions concerning Neanderthals that hitherto could be studied exclusively by morphological and archaeological approaches. For example, the genetic relationship between Neanderthal populations in Europe and in western Asia could be explored, as could the demographic history of Neanderthal populations.
-Why did the researchers wear protective clothing and note so emphatically that they did so?

A) They needed to minimize the chance of introducing their own mitochondrial DNA to the sample.
B) They needed to be certain there were no ancient pathogens on the sample that modern humans hadn't been exposed to.
C) They needed to be sure not to harm the precious sample with oils from skin or moisture from their breath.
D) Because the work was done in Germany, they needed to follow stringent, standard German laboratory procedures and document their compliance.