Under which of these conditions would scientists use the polymerase chain reaction (PCR) before they analyze a DNA sample? A The DNA sample comes from a bacterium or virus.

B
The DNA sample has been cut into fragments by restriction enzymes.

C. Only a small amount of the DNA sample is available

D. The DNA sample includes regions that are transcribed into mRNA.

your answer should be c) enjoy!

the last one: artificial selection/genetic engineering

plant breeding is modifying the genetic composition of the plant - but this isn't cloning (which is specifically introducing a gene into a genome). but you are artificially selecting for the phenotype that you want.

the second one is literally genetic engineering - the gene would have been cloned first and then inserted or genetically engineered into the new plant cell (the cotton).