题干

某元素X的气态氢化物的化学式为H2X,则X的最高价氧化物的水化物的化学式为(   )

A:H2XO3

B:HXO3

C:H3XO4

D:H2XO4

上一题 下一题 0.0难度 选择题 更新时间:2011-11-11 10:36:07

答案(点此获取答案解析)

D

同类题2

阅读下面的文字,完成下列小题

卫生餐厅

(美)约翰·爱伦

    “来两只嫩煮鸡蛋,一客家常油炸土豆条,一块乌饭浆果松饼,再加咖啡和鲜桔汁。我吩咐卫生餐厅的侍者,慢跑后的我感到饥肠辘辘。

    我刚打开报纸,咖啡就端上来了。“请用咖啡,”侍者说。“不过,对不起。我们的立法当局坚持要我们提醒顾客,每天喝三杯以上的咖啡有可能增加得中风和膀胱癌的危险。虽然这是除去了咖啡因的,但食品和药物管理局仍要求我们说明,提取过程中或许还残留了微量的致癌可溶物。”这才给我的杯子斟上。

    侍者端着我叫的早点回来时,报纸差不多看完了第一版。

    “您的鸡蛋,”侍者说,“如果不煮透,就可能含有沙门氏菌,会引起食物中毒。蛋黄中有大量的胆固醇,它有诱发动脉硬化和心脏病的主要潜在危险。美国心血管外科医生协会主张每星期至多只吃四个鸡蛋,吸烟者和身体超重十磅者尤应如此。”

    我的胃感到一阵不舒服。

    “马铃薯,”侍者继续着,“皮上的青色斑块有可能含有一种叫龙葵的生物碱毒素,《内科医生参考手册》上说龙葵碱会引起呕吐、腹泻、恶心。不过放心,您用的土豆是仔细地去了皮的,我们的供应商还答应,如有不良后果,他们将承担一切责任。”

    “但愿这‘不良后果’别降临到我头上。”我想。

    “松饼含有丰富的面粉、鸡蛋和黄油,还有乌饭浆果和低钠调味粉,唯独缺少纤维素。营养研究所警告说低纤维饮食会增加胃癌和肠癌的危险。饮食指导中心说面粉可能受到杀真菌剂和灭鼠剂的污染,可能含有微量的麦角素,它能引起幻觉、惊厥和动脉痉挛。”

    顿时,我觉得焦黄松脆的松饼诱人的香味变得十分可疑了。

    “黄油是高胆固醇食品,卫生部忠告近亲患心脏病的人限制胆固醇和饱和脂肪的摄入量。我们的乌饭浆果来自缅因州,从未施过化肥和杀虫剂。但美国地质调查队有报告说许多缅因州的浆果长在花岗岩地区,而花岗岩常常含有放射性物质铀、镭和氡气。”

    我立刻想起了切尔诺贝利事故幸存者头发脱落的不雅观之状。

    “最后,烘焙的麦粉中含有硫酸铝钠盐,研究者认为铝元素可能是早老性痴呆症的罪魁祸首。”侍者说罢便离去了,令人肃然起敬的营养科普也许结束了。

    侍者很快回来了,带着一只罐子。“我还记得说明,我们的鲜桔汁是早上六点前榨的,现在是8:30正。食物和药品管理局与司法部正在指控一家餐馆,因为它把放了三四小时的桔汁说成是新榨的。在那个案子裁决前,我们的律师要求我们从每一个订了类似食品的顾客那儿弄一份放弃追究声明书。”

    我填写了他递过来的表格,侍者用回形针把它附在账单上。在我伸手取杯子时,侍者又拦住了。“还有一件事”,侍者说,“消费安全组织认定您使用的叉子太尖太锋利,必须小心使用。

    “好,祝您胃口好。”侍者终于走开了,艾德沃德也终于松了一口气。他拨拉着已是冷冰冰的那份早餐,胃口彻底倒了。哦!上帝!

同类题3

   A 10-year-old boy decided to learn judo though he had lost his left arm in a car accident. The boy was doing well, so he couldn't understand why, after three months of training, the master had taught him only one move.
   “ Master,” the boy finally asked, “shouldn't I be learning more moves?"“ This is the only move you know, but this is the only move you'll ever need to know,” the teacher answered.
   Several months later, the teacher took the boy to his first competition. Surprising himself, the boy easily won his first two matches. The third match proved to be more difficult, but after some time, his opponent (对手) became impatient and charged; the boy skillfully used his one move to win the match. Still amazed by his success, the boy was now in the final.
  This time, his opponent was bigger, stronger, and more experienced. Soon after the match started, the boy seemed to lose. Thinking that the boy might get hurt, the judge called a time-out. He was going to stop the match when the teacher appeared. “ No,” the teacher said, “Let him continue.” A short time after the match carried on, his opponent made a careless mistake. At once, the boy used his move to pin (压住) him. The boy won the match and the competition.
  On the way home, the boy asked the teacher what was really in his mind. " Why could I win the competition with only one move?" The teacher answered. "First, you've mastered one of the most difficult throws in judo. Second, your opponent can only attack your left arm to win you.”
根据短文内容完成下面的表格,每空一词。

Title: One’s weakness can become his____ 
A boy had lost left arm, ____  he decided to learn judo
After three months of training, the master taught him only one move.
His first____ First three matchesHe won.
FinalHis opponent was bigger, ____  and more ____ .
At the ____ , the boy seemed to lose the match.
The judge was____  that the boy might get hurt and called a time-out.
His opponent made a mistake. The boy used his move and pinned him.
He became the ____  of the match.
____ 1. He had almost mastered one of the most difficult throws in all of judo.
 The opponent can win the match by ____  your left arm.