When the author says that "Ceren' s architecture, crafts, and agriculture were surprisingly sophisticated and varied.", he means ______.

A．because grasses that made up the thatched roof of the dwelling were still new, that the structure was recent
B．he left the site, located northwest of San Salvador, the capital, in 1980 unwillingly
C．by sending radar signals through the ground in order to detect buried objects, he located 22 additional structures still buried in ash
D．when the teeth were found, he said that throwing teeth on the roof is a tradition still practiced by some people in rural El Salvador today

A．Each page can be given a score that reflects its importance.
B．In the beginning of rating a page's relative importance, all pages are given the same score.
C．The importance of one page depends on the importance of pages that link to it, the importance of which depends in turn on the importance of pages that link to them.
D．One page's score is given totally to another page it links to.