问题 选择题

下列各项图象表示中,正确的是(  )

A.

等质量的Mg、Zn、Fe与足量的稀盐酸反应

B.

     用NaOH溶液逐滴HCl中

C.

小梅绘的NaCl与Ca(OH)2溶解度曲线

D.

恒温向接近饱和的NaCl溶液加入NaCl固体

答案

A、依据不同金属与酸反应制得氢气的质量为

金属的化合价
金属的相对原子质量
×金属的质量可知:等质量的镁铁锌与足量的稀盐酸反应时生成的氢气质量关系为:Mg>Fe>Zn,观察图象符合该特征故正确;

B、盐酸溶液的pH小于7,氢氧化钠的溶液pH大于7,随着氢氧化钠的滴入盐酸不断消耗pH不断变大,直至恰好反应pH=7,再滴加pH会大于7,观察图象不符合该过程中pH的变化;

C、氯化钠的溶解度随温度升高变化不明显,而氢氧化钙的溶解度随温度的升高而降低,图示两者的溶解度随温度变化的情况与事实不符;

D、接近饱和的氯化钠溶质质量分数不能为零,且恒温下向接近饱和的NaCl溶液加入NaCl固体时氯化钠溶液的溶质质量分数会不断变大直至溶液饱和后溶液的溶质质量分数不再升高,图象与事实不符;

故选A

阅读理解

Not everyone goes to university after high school graduation. Some work, others join the army and an increasing number worldwide are taking a “gap year” to travel or do community service in their own countries or abroad. They are studying sharks off the Australian coast, building schools in Mexico and learning Spanish or Italian.

The concept of a gap year may not be new, but the recent surge (涌现) of interest certainly is.  Some students are putting off admissions. Others, who don’t get into the college of their choice, are taking a year to explore new frontiers before reapplying.

Students are choosing to take a breather; they are thinking. They are not sure what they are going to do. They are going and exploring some of their interests. They are getting experience they can take to the school they finally go to.

It is an idea actively encouraged by colleges. Princeton University has just launched a “bridge year” program that will send 10 percent of its incoming class to do volunteer work abroad, starting in 2009. And the Harvard has spent the last 30 years urging incoming students to take a gap year.

“Many speak of their year away as a ‘life-changing’ experience or a ‘turning point’” says Harvard admissions director Marlin Lewis. “Many come to college with new opinions about their academic plans, their extracurricular interests and the career possibilities they observed in their year away.”

小题1:The reasons why some take a gap year are the following EXCEPT that ________.

A.they hate studying

B.they don’t know what to do

C.they want to get experience

D.they want to know their real interests小题2:A student won’t ________ in a gap year.

A.travel

B.join the army

C.do community service

D.learn a foreign language小题3:After a gap year, one would probably _________.

A.take another year off

B.earn a lot of money

C.be refused by his college

D.have new ideas about their future career小题4:From the passage we know that ________.

A.more and more students will take a gap year

B.fewer and fewer colleges will encourage his students to take a gap year

C.the gap year can only give one some experience about society

D.nobody will change his own interests after the gap year

单项选择题

①科学家已经分离出一种看起来能决定人体衰老速度的基因序列。这一发现首次将DNA与人类寿命联系起来。②这项研究有望为创建筛查程序铺平道路,可用于检验哪些人更容易衰老,并在年轻时更容易患心脏病或其他疾病。③尽管这项突破不太可能带来大幅延长人类寿命的药物,但也许有助于延长那些由于自身基因而更易早逝的病人的寿命。④这项研究显示出了时间性衰老和生物性衰老的区别,其中生物性衰老取决于人体基因组成和生活方式,比如饮食组成和是否吸烟;两个年龄相同的人,其生物年龄可能会有十多年差异。⑤由桑尼教授带领的研究小组发现,一段普通DNA序列与人体的生物性衰老有密切关系。对近三千人的研究显示,约有38%的人带有遗传性基因变体,与没有这一基因序列的人相比,他们的生物年龄要老三到四岁;占总数7%的人带有两个这种基本变体,他们的生物年龄比没有该变体的人要老六到七岁。⑥通常被认为是老年病的发病年龄有很大的[ ],正是这一点促使研究者展开了这项研究。⑦我们身体中的大部分细胞都含有叫作染色体的DNA分子链。染色体在其两端有保护帽,叫做端粒。细胞每次分裂时,端粒会缩短,就像鞋带两端的塑料会被磨损一样。当端粒变得非常短时,细胞就无法正常工作,会显现衰老的征兆。⑧通过对血液样本的分析,桑尼发现,这些人具有与其年龄不相称的过短染色体端粒。而一种特定的基本序列在这些人中更常见。这段DNA位于3号染色体,与基因TERC相邻。⑨基因TERC可以制造出一种酶,能在端粒缩短时对端粒进行修复。携带有一个或两个该基因序列的人,在母体子宫中发育时,制造出的这种酶(端粒酶)可能比较少。这意味着,这些人在出生时端粒就比较短,所以更容易衰老。⑩科学家不可能通过增加人体中的端粒酶的数量来逆转人体老化的过程。人出生后,体内的端粒酶几乎全处于被抑制状态,但在癌细胞中端粒酶被激活,所以癌细胞就会无限分裂下去而不会死亡。因此桑尼指出:“激活端粒酶也许可以让你不得心脏病,但如果不加控制地激活端粒酶,你也许会得癌症。”

与文中提到影响人生物性衰老的因素无关的一项是( )。

A.是否抽烟

B.饮食组成

C.特定基因

D.母体子宫