Hi there!
The answer is C.
The different colored layers of the Grand Canyon took thousands of millions of years to form. Each layer represents one time period, and each is unique.
Hope this helps!
Answer:
Because Tay Sachs is a recessive gene.
Explanation:
It takes two donors both with a recessive gene for the gene to express itself. In this case, two people both with the recessive Tay Sachs disease would have to have children. But when people marry who have the trait, the recessive gene, the recessive can be passed on through to the next generation and so on.