The northern blot technique is used for the detection of
A. protein
B. DNA
C. RNA
D. All of the above

Hint: The set of techniques that enable the DNA from different sources to be identified, isolated, and recombined is Recombinant DNA technology (genetic engineering). One can define the term recombinant DNA technology as to how genetic material from one organism is artificially introduced into another organism's genome. Thus, we can say that new characteristics can be introduced into an organism. And that credits will be received by Paul Berg, Herbert W Boyer, and Stanley N Cohen, although many other scientists made significant contributions to the new technology.

Complete answer:
Protein: Western blot is an invaluable lab technique used to detect proteins in a tissue or a blood sample.
DNA: Individual's DNA characteristics can be determined by DNA profiling(DNA fingerprinting) most effectively.
RNA: Northern blots protocols begin with RNA isolation, and separation techniques vary depending on RNA size. Large RNAs are separated by electrophoresis on a formaldehyde agarose gel or glyoxal agarose gel, which prevents regular base pairing and maintains RNA as a denatured state. Small RNAs are separated on a denaturing (urea) polyacrylamide gel. The nylon membrane gets RNA from the gel, then incubated with radioactivity or non isotopically labeled RNA, DNA, or oligodeoxynucleotide probes. Washing with a buffer removes the unhybridized search. Radiolabeled probes and enzymatically labeled probes are visualized with X-ray film and chemiluminescence, respectively.
So, the correct answer is “Option C”.

Note:
Before the discovery of ribozymes, enzymes were only the catalytic proteins. In 1989, Thomas R. Cech and Sidney Altman got the Nobel Prize in chemistry to discover the catalytic properties of RNA. RNA also acted as genetic material and was termed as genetic RNA. Most of the RNA present in organisms is non-genetic. RNA with catalytic activity is termed as a ribozyme (ribonucleic acid enzyme). RNA molecules play essential roles in transforming genetic transformation during protein synthesis and the control of gene expression. The diverse functions of RNA molecules in living organisms also include catalytic activity and genetic information storage.