To find the lcm of 30,40 show work

Q: a: in sexually reproducing animals, once fertilization of the egg takes place, the exists as a single cell until cell division begins

This comparative chart is an example of one that might be used by scientists and law enforcement personnel for identification purposes. the chart represents a technological advance called

Ialready know the answers to these questions and they are on the attachment. but i just need to know why that answer is the correct one. plz asap! this is for a report that i need to email by 10!