Why was PCR amplification of the 35S promoter from the cauliflower mosaic virus chosen as the means to detect whether or not a food has been genetically modified ?

Polymerase Chain Reaction (PCR)

Explanation:

Note that Polymerases Chain Reaction (PCR) is used to amplify food DNA to test for the presence of genetically modified DNA in food products because usually DNA fragments can be isolated from highly processed goods and are sufficiently intact to be amplified by PCR.

The process used by Genetic engineers is called  gel electrophoresis where only a small number of regulatory sequences (promoter and terminator sequences) are used to control the expression of the inserted genes.

the answer is b.) hydrogen bonds between bases.