I think the answer is B or D because in choice A there is no way that 8 to get up to 10 and 10 can go down to 8. In choice C, there is no way that 8 can become 5 and 10 to become 4. In choice D, 8 can become 4 by dividing by 2. This can also happen from 10 to 5 by diving by 2. I hope this helps!
