沙特阿拉伯主要的经济来源是（  ）

阅读答题。
                                                                                       【甲】 江城子密州出猎
                                                                                                        苏轼
                                     老夫聊发少年狂，左牵黄，右擎苍。锦帽貂裘，千骑卷平冈。为报倾城随太守，亲射虎，看孙郎。
                                     酒酣胸胆尚开张，鬓微霜，又何妨，持节云中，何日遣冯唐？会挽雕弓如满月，西北望，射天狼。
                                                                                        【乙】   东栏梨花
                                                                                                        苏轼
                                                                              梨花淡白柳深青，柳絮飞时花满城。
                                                                              惆怅东栏一株雪，人生看得几清明！