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

Option (D).

Explanation:

Dolly was the first sheep cloned in the year 1997. The sheep has been cloned from the adult somatic cells. The sheep was cloned by  Keith Campbell, Ian Wilmut.

The adult's cell nucleus was fused with the enucleated sheep egg. The egg was then incubated in the surrogate female. The telomeres of Dolly sheep was found to be shorter than the normal individuals.

Thus, the correct answer is option (D).

it will increase due to the time span

a. by using fur or clothes to trap heat energy near the body