Why Was the Nucleus Removed from the Egg Cell Used

Why was the nucleus removed from the egg cell used to create Dolly, the cloned sheep?

A) to remove the mitochondrial DNA of the egg donor
B) to test whether the genetic contribution from a sperm cell alone could produce a lamb
C) to create a cloned sheep in the absence of DNA
D) since the genome for the clone was supplied by the diploid mammary cell, the presence of the egg cell DNA would result in triploidy
E) to see whether egg cell DNA injected into a sperm cell could produce a lamb