《美国化学会志》报道了中国科学家以二氧化碳和钠在一定条件制得金刚石的实验事实，其化学方程式为3CO₂+4Na = 2X+C（金刚石）。则上述反应中X的化学式为（）

    顷之未发，太子迟之，疑其有改悔，乃复请之曰：“日以尽矣，荆卿岂无意哉?丹请先遣秦武阳！”荆轲怒，叱太子曰：“今日往而不反者，竖子也！今提一匕首入不测之强秦，仆所以留者，待吾客与俱。今太子迟之，请辞决矣！”遂发。

    太子及宾客知其事者，皆白衣冠以送之。至易水上，既祖，取道。高渐离击筑，荆轲和而歌，为变徵之声，士皆垂泪涕泣。又前而为歌曰：“风萧萧兮易水寒，壮士一去兮不复还！”复为慷慨羽声，士皆瞋目，发尽上指冠。于是荆轲遂就车而去，终已不顾。

    既至秦，持千金之资币物，厚遗秦王宠臣中庶子蒙嘉。

    嘉为先言于秦王曰：“燕王诚振怖大王之威，不敢兴兵以拒大王，愿举国为内臣，比诸侯之列，给贡职如郡县，而得奉守先王之宗庙。恐惧不敢自陈，谨斩樊於期头，及献燕之督亢之地图，函封，燕王拜送于庭，使使以闻大王。唯大王命之。”

    秦王闻之，大喜。乃朝服，设九宾，见燕使者咸阳宫。

    荆轲奉樊於期头函，而秦武阳奉地图匣，以次进。至陛下，秦武阳色变振恐，群臣怪之，荆轲顾笑武阳，前为谢曰：“北蛮夷之鄙人，未尝见天子，故振慑，愿大王少假借之，使毕使于前。”秦王谓轲曰：“起，取武阳所持图！”

    轲既取图奉之，发图，图穷而匕首见。因左手把秦王之袖，而右手持匕首揕之。未至身，秦王惊，自引而起，绝袖。拔剑，剑长，操其室。时恐急，剑坚，故不可立拔。

    荆轲逐秦王，秦王还柱而走。群臣惊愕，卒起不意，尽失其度。而秦法，群臣侍殿上者，不得持尺兵；诸郎中执兵，皆陈殿下，非有诏不得上。方急时，不及召下兵，以故荆轲逐秦王，而卒惶急无以击轲，而乃以手共搏之。

    是时，侍医夏无且以其所奉药囊提轲。秦王方还柱走，卒惶急不知所为。左右乃曰：“王负剑！王负剑！”遂拔以击荆轲，断其左股。荆轲废，乃引其匕首提秦王，不中，中柱。秦王复击轲，被八创。

    轲自知事不就，倚柱而笑，箕踞以骂曰：“事所以不成者，乃欲以生劫之，必得约契以报太子也。”

    左右既前，斩荆轲。秦王目眩良久。

根据短文理解，选择正确答案。

    The 87^th Academy Award nominations（提名）were announced on Jan 15,and The Grand Budapest Hotel stood out as a favorite with nine nominations, including Best Picture. Check out some other Best Picture nominees to see if you missed any of last year's top Hollywood films.

The Imitation Game

    This historical thriller is about British computer scientist, Alan Turing (Benedict Cumberbatch), the father of artificial intelligence. At the start of World War Ⅱ, Turing was asked to join a select team of mathematical geniuses to decode（解码）the system the Nazis used to send military messages. Besides the actual breaking of the code, Cumberbatch's portrayal（扮演）of Turing's personality, a mixture of decency（正派）and shyness, is also a highlight of the movie.

Birdman

    This dark comedy film is about how Riggan Thomson, a faded star once famous for his superhero roles, struggles to regain fame. American actor Michael Keaton, 63, who has a similar experience to Thomson's, plays the leading role.

Selma

    A stellar cast(主要演员) including talk show queen Oprah Winfrey may be one reason to see Selma. But that the film focuses on Martin Luther King Jr.'s struggle for civil rights also makes it worth viewing. Based on the 1965 Selma to Montgomery voting rights marches, the film is a chronicle(编年史) of King's(David Oyelowo) campaign for political rights for African-American people.

The Theory of Everything

    We know English theoretical physicist Stephen Hawking for his significant scientific discoveries, especially his black hole theories. This biographical film reveals the scientist's (played by Eddie Redmayne) secret romantic relationship with Jane Hawking (Felicity Jones), whom he meets and falls in love with at Cambridge and who later becomes his first wife.

Boyhood

    American Director Richard Linklater did an experiment in this film, using the same cast for l2 years to record a boy's growth. In two and a half hours, we see Mason, a Texas boy from a divorced family, grow from 6-year-old boy to a freshman in college.