In 1997, dolly the sheep was cloned. which of the following processes was used?
a. use of mitochondrial dna from adult female cells of another ewe
b. replication and dedifferentiation of adult stem cells from sheep bone marrow
c. separation of an early-stage sheep blastula into separate cells, one of which was incubated in a surrogate ewe
d. fusion of an adult cell's nucleus with an enucleated sheep egg, followed by incubation in a surrogate