(D) The foreign DNA is isolated by restriction enzymes.
Step-by-step explanation:
BT corn is a type of genetically modified organism. While creating a BT corn, the gene of interest is inserted into the host cell. In BT corn, the gene of interest is taken from a bacterium, Bacillus thuringiensis. In the first step, the gene of interest is being isolated by the restriction enzyme. The restriction enzymes are those enzymes that detects particular DNA sequences and cuts it in that specific site therby providing more accuracy.