Mutation. A mistake made while DNA copies which causes changes in DNA
That is not the correct answer
Answer: Layer a is 500 million years old.
Explanation:
Trilobite is a member of the group of extinct arthropods found as fossils and they can be identified by the three-lobed as well as three segmented forms. These were the marine animals. These were appeared initially in the Cambrian Period. They used to live 542 million years ago so the fossils can be estimated to be aged of 500 above years old. These animals used to dominate in the sea area.
Dolly was a female fin Dorset sheep,
Although it has been claimed that dolly had 3 mothers. one provided the egg, another the DNA, and a third carried the cloned embryo to term.
So therefore, dolly has the genes of different species of sheeps.
Hope this helped!
The purpose of an indicator is to test how acidic or basic something is.