What does "brainchild" in the paragrapth 4 mean

A．the worship of the sun-god had clearly been the function of the temple
B．all living things celebrate the sunrise
C．the sunrise is the most magnificent of all phenomena
D．It is natural for man to worship the sun and he has always done so

A．had been abandoned by the Mayas about thirteen hundred years previously
B．had been occupied and developed by the Mayas about thirteen hundred years before
C．had been deserted by the Mayas as soon as the Spaniards arrived
D．was conquered by the Mayas thirteen hundred years ago