Read the following paragraph and answer the given questions.

RNAi takes place in all eukaryotic organisms as a method of cellular defense. The source of this complementary RNA could be from an infection by viruses having RNA genomes or mobile genetic elements (transposons) that replicate via an RNA intermediate. Insulin from an animal source, though caused some patients to develop allergy or other types of reactions to the foreign protein. Insulin consists of two short polypeptide chains: chain A and chain B, that are linked together by disulphide bridges. Transgenic mice are being developed for use in testing the safety of vaccines before they are used on humans. Transgenic mice are being used to test the safety of the polio vaccine. If successful and found to be reliable, they could replace the use of monkeys to test the safety of batches of the vaccine. Specific Bt toxin genes were isolated from Bacillus thuringiensis and incorporated into the several crop plants such as cotton. The choice of genes depends upon the crop and the targeted pest, as most Bt toxins are insect-group specific. The toxin is coded by a gene cry/Ac named cry. There are a number of them, for example, the proteins encoded by the genes cry/Ac and cryllAb control the cotton bollworms, that of crylAb controls corn borer.

The suitable example of mobile genetic elements is :

Transposons

The correct answer is Option (3) → Transposons

Transposons, also known as "jumping genes," are mobile genetic elements that can move from one location to another within a genome. Transposons can change positions on chromosomes, which can lead to mutations, changes in gene expression, and genome rearrangements. They are important in genetic diversity and evolution.

Transposons work by copying and inserting themselves into new positions within the genome, or they may directly "cut" and "paste" themselves into different locations.