請依下文回答第 31 題至第 35 題：Mada’in Saleh was known as Hegra by the Nabataean people who carved its magnificent tombsinto the golden Quweira sandstone outcrops. They were also known for their incredible familiarity withthe desert and their ability to fade into it to evade enemy tribes. Their system of hidden cisterns dugdeep in the interior provided water for their livestock and their people. The real cause of the success ofthe Nabataeans, however, was control over much of the spice trade. Many spices from southern Arabiawere brought up to the north along trade routes to be purchased by people around the Mediterranean andin the Near East.The details on the entrance portals and the smooth surfaces of its 111 tomb façades reflect the greatskills of the masons of the Nabataeans’ time. The splendor of the natural setting here must havereminded the Nabataeans of their capital, Petra. It is no wonder that they chose this very spot to buildtheir second city, Hegra, because it was a crossroads where the major north-south incense routeintersected a road from the Red Sea to the Persian Gulf.The ruins of the town of Hegra lie on the plain some distance from their tombs. The buildings, stillfor the most part unexcavated, were made of unimpressive sun-dried mudbrick. What is known aboutHegra comes primarily from the tombs, the many inscriptions carved into their façades, and referencesfound elsewhere. The tomb façades are finely carved and fairly uniform in their style. A portal in thecenter of the façade provides the entrance to the tomb. Inside are recesses carved into the walls wherethe bodies of the deceased were placed.
31 What is this passage mainly about?
(A)How the Nabataeans sold spices in ancient times.
(B)How the ruins of Hegra reveal the Nabataeans’ lives.
(C)How people made a living in the desert.
(D)How the Nabataeans carved their tombs.