Why do we not know if any dynasties preceded the shang?

What was the purpose of the "bay of pigs" mission

At the casablanca conference, allied leaders signed an agreement to share military technology decided to launch an invasion of southern france agreed to accept only the unconditional surrender of the axis powers agreed to form a scientific team to create the atomic bomb

Which of the following cultures were among the earliest known inhabitants of north america? a) mayab) incac) anasazi d) olmec