Petra

(1) there are many examples of grand architecture in the world. (2) some of the most impressive are buildings of the ancient city called petra in jordan. (3) petra is the greek word for "rock." (4) the early inhabitants of petra—the nabataeans—did not use wood or brick to make the structures, but instead, they carved them right out of the desert sandstone cliffs.
(5) two thousand years ago, petra was an important center of activity where caravans of travelers would pass through on their way to trade goods in other regions. (6) their power and riches can still be seen today in the remains of their city.
(7) although petra was built in a rugged, dry desert, the nabataeans made wise plans for collecting and storing water. (8) this water system was made of cisterns, or reservoirs, that held water and channels that directed water from one place to another.
(9) after thriving for about 1,000 years, petra began to decline. (10) the trade routes that had once gone through the city were changed to go toward the sea. (11) in addition, an earthquake devastated the area. (12) the ruins of the city were rediscovered in the 1800s by a european traveler who disguised himself as a local bedouin, or local middle eastern person, to find the remote location.
(13) today, modern travelers can visit petra and see its majesty in person; tours are available by foot, donkey, or camel. (14) much of petra remains to be seen; archaeologists have uncovered only 15 percent of it. (15) the rest of this city is still "lost" or underground.

4. where would the following sentence best fit in the passage?

because of this advanced system by the nabataeans, many gardens flourished in petra.
a-after sentence 8
b-after sentence 13
c-after sentence 10
d-after sentence 9