In many waterways around the United States, poly-chlorinated biphenyls (PCBs) have contaminated the sediments and wildlife. Given that most of the PCBs in the environment were released before 1980 and are still present in these ecosystems. What best describes this phenomenon?

Long persistence

Explanation:

Poly-chlorinated biphenyls (PCBs) are organic chlorine compounds which were once widely used in coolants and heat transfer fluids. Their manufacture was banned in many places once it was found out that they are potential carcinogens. They are also classified as Persistent Organic Pollutants.

However, even today they can be detected in many ecosystems. It is because they have long persistence owing to their chemical structure. They are resistant to degradation by both acids and bases. They are also not prone to oxidation or hydrolysis. Temperature change also does not impact their structure. Hence, they can persist in the environment for a long time.  

many phylogenetic trees have a single lineage at the base representing a common ancestor. a lineage that evolved early from the root and remains unbranched is called basal taxon. when two lineages stem from the same branch point, they are called sister taxa.

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explanation:

blue stars have the highest surface temp

stellar distances are usually expressed in light-years

the measure of a star's brightness is called magnitude

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