Several companies now offer DNA "banking services," where DNA is extracted from a pet and is stored so that a "replacement pet" might be produced using cloning techniques when the original pet dies. Which statement best explains why the replacement pets that are produced in this way might not look or act like the original?
a. The new animal must get the DNA from two different parents, not just one cell
b. Mutations could occur that change the cloned animal into a completely different species
c. Recombination of the cells as they are cloned will make the resulting pet act differently
d. The environment could influence how genes are expressed, changing how the animal looks and acts.