100 POINTS PLEASE ANSWER- the answer is not c or d CONFIRMED

The diagram illustrates the process of developing genetically modified corn.

What occurs at step 3 in the diagram?
The restriction enzymes cut the isolated DNA into fragments.
The gene of interest is inserted into an expression cassette.
The recombinant DNA is inserted into the host cell nucleus via a vector.
The expression cassette is inserted into a plasmid for cloning.