Read the excerpt from "Egyptian Tombs: A Grave Matter.” The pharaohs were aware of these crimes, so they took precautions. Many had their pyramids constructed with twisting pathways and decoy chambers. Only one secret passage led to the real tomb, and that was sealed off with huge granite blocks. Often guards were employed as well. Severe punishment awaited thieves who were caught, since the Egyptians considered grave robbery an outrageous crime.

None of the pharaohs’ precautions stopped the thieves, however. Eventually, they realized that they needed a new place for burial—a place that would protect their bodies and treasure for all of eternity. They found it in the Valley of the Kings, a barren area that was difficult to travel to. The pharaohs began putting underground tombs there in the sixteenth century BCE.

Based on the sequence of events in the excerpt, which sentence best states a cause-and-effect relationship?

Because so many graves were robbed, grave-robbing was considered a terrible crime.
Because none of the precautions they took were effective, the pharaohs found a new burial ground in the Valley of the Kings.
Because the graves were so heavily protected, there were very few instances of grave robberies in ancient times.
Because there was only one way to enter most burial chambers, grave robbers were often stopped.