Which of the following is evidence for how the composition of the atmosphere has changed on earth over time?

a. bands of iron found in rock layers show that the earth's atmosphere became oxygenated by photosynthetic cyanobacteria millions of years ago.
b. frequent volcanic eruptions have caused the earth's atmosphere to fill with sulfur aerosols dropping the temperature globally by 5 degrees.
c. multiple ice ages in the 18th century have caused a shift in atmospheric circulation on present day earth.
d. over the past 50 years, greenhouse gas concentrations have rapidly decreased in the atmosphere.

ans.

dna fingerprinting is defined as a process that determines the dna characteristics of an individual. these dna characteristics are unique among individuals as their fingerprints, so it is known as dna fingerprinting.

steps of dna fingerprinting includes extraction of dna from sample, amplification of dna, restriction digestion of amplified dna, and then analysis of dna by gel electrophoresis, respectively.

thus, the next step performed by the scientist is 'to cut the amplified dna (obtained by polymerase chain reaction) by restriction enzymes that cleave the dna into fragments and their analysis.'