为了保证教学实验顺利进行，学校选用教学经验丰富、认真负责的老师负责用改进的方法教"实验1班"和"实验2班"的数学，另外随机选择老师用传统方法教"普通1班"和"普通2班"的数学，实验班和普通班的学生随机分配。结果实验班各科成绩都显著高于对照，研究结论是改进的方法不仅能提高学生数学成绩，而且能全面改善学生的学习，值得推广。

如果班级的称谓对研究的内部效度有影响，从性质和来源上看，该影响属于

A:历史因素 B:选择因素 C:成熟因素 D:测量和测试手段 E:实验处理和程序

Dangers Await Babies with Altitude

    Women who live in the world’s highest communities tend to give birth to underweight babies, a new study suggests. These babies may grow into adults with a high risk of heart disease and strokes.¹

    Research has hinted that newborns in mountain communities are lighter than average. But it wasn’t clear whether this is due to reduced oxygen levels at high altitudes or because their mothers are under-nourished — many people who live at high altitudes are relatively poor compared with those living lower down.

    To find out more, Dino Giussani and his team at Cambridge University studied the records of 400 births in Bolivia during 1997 and 1998. The babies were bom in both rich and poor areas of two cities: La Paz and Santa Cruz. La Paz is the highest city in the world, at 3.65 kilometers above sea level, while Santa Cruz is much lower, at 0.44 kilometers.

    Sure enough, Giussani found that the average birthweight of babies in La Paz was significantly lower than in Santa Cruz. This was true in both high and low-income families. Even babies bom to poor families in Santa Cruz were heavier on average than babies born to wealthy families in lofty La Paz. “We were very surprised by this result,” says Giussani.

    The results suggest that babies bom at high altitudes are deprived of² oxygen before birth. “This may trigger the release or suppression of hormones that regulate growth of the unborn child,³ ”says Giussani.

    His team also found that high-altitude babies tended to have relatively larger heads compared with their bodies⁴. This is probably because a fetus starved of oxygen will send oxygenated blood to the brain in preference to the rest of the body.⁵

    Giussani wants to find out if such babies have a higher risk of disease in later life. People born in La Paz might be prone to heart trouble in adulthood, for example. Low birthweight is a risk factor for coronary heart disease. And newborns with a high ratio of head size to body weight are often predisposed to high blood pressure and strokes in later life.

词汇：

altitude / ’æltɪtju:d /n．维度，（海拔）高度

stroke /strəʊk / n．中风

birthweight n．出生体重

coronary / ’kɒrənəri /adj．冠状的

under-nourished adj．营养不足的

underweight /’ʌndəweɪt / adj．重量不足的

hint / hɪnt / vt．暗示

hormone /’hɔ:məʊn / n．荷尔蒙

fetus / ’fi:təs / n．胚胎

注释：

1．... grow into adults with a high risk of heart disease and strokes：……长大成人后得心脏病和中风的风险很大

2．... are deprived of ...：被剥夺了……，缺乏……

3．This may trigger the release or suppression of hormones that regulate growth of the unborn child：这可能会触发调节未出生儿成长的荷尔蒙的释放或抑制。这里的release是名词。

4．relatively larger heads compared with their bodies：相对身体来说较大的头部

5．... a fetus starved of oxygen will send oxygenated blood to the brain in preference to the rest of the body：……一个缺乏氧的胚胎会首先把充氧的血液输送到脑部，然后才送到身体的其他部位。starved of是分词短语，修饰fetus, in preference to表示的是第二位的选择，如：I chose to study English in preference to Russian in university.读大学时，我选了英语，而不是俄语。

Giussani did not expect to find that the weight of a baby had little to do with the financial conditions of the family he was bom into.

A:Right  B:Wrong C:Not mentioned

                                                                                                                                        偃虹堤记
    有自岳阳至者，以滕侯^【1】之书、洞庭之图来告曰：“愿有所记。”予发书按图，自岳阳门西距金鸡之右，其外隐然隆高以长者，曰偃虹堤。问其作而名者，曰：“吾滕侯之所为也。” 问其所以作之利害，曰：“洞庭，天下之至险；而岳阳，荆、潭、黔、蜀四会之冲也。昔舟之往来湖中者，至无所寓，则皆泊南津，其有事于州者远且劳，而又常有__之恐、覆溺之虞。今舟之至者，皆泊堤下，有事于州者近而且无患。”问其大小之制、用人之力，曰：“长一千尺，高三十尺，厚加二尺，用民力万有五千五百工，而不逾时以成。”问其始作之谋，曰：“州以事上转运使，转运使择其吏之能者行视可否，凡三反复，而又上于朝廷，决之三司，然后曰可，而皆不能易吾侯之议也。”曰：“此君子之作也，可以书矣。”

    盖虑于民也深，则其谋始也精，故能用力少而为功多。夫以百步之堤，御天下至险不测之虞，惠其民而及于荆、潭、黔、蜀，凡往来湖中，无远迩之人皆蒙其利焉。且岳阳四会之冲，舟之来而止者，日凡有几！使堤土石幸久不朽，则滕侯之惠利于人物，可以数计哉？夫事不患于不成，而患于易坏。盖作者未始不欲其久存，而继者常至于殆废。自古贤智之士，为其民捍患兴利，其遗迹往往而在。使其继者皆如始作之心，则民到于今受其赐，天下岂有遗利乎？此滕侯之所以虑，而欲有纪于后也。

    滕侯志大材高，名闻当世。方朝廷用兵急人之时，常显用之。而功未及就，退守一州，无所用心，略施其余，以利及物。夫虑熟谋审力不劳而功倍作事可以为后法一宜书不苟一时之誉思为利于无穷而告来者不以废二宜书岳之民人与湖中之往来者皆欲为滕侯纪三宜书以三宜书不可以不书，乃为之书。

    庆历六年某月某日记。

                                                                                                                                                                                                     （取材于《欧阳文忠公集》）
    注释：【1】滕侯：即滕子京，北宋人，屡遭贬黜，其时被贬，任岳州知州。

A:文章认为，滕侯对偃虹堤的周密策划和精心施工，是出于他对百姓深切的关怀和热爱。 B:古代不少利国利民的工程，由于年深日久缺乏维护，往往成了废弃的遗迹，令人遗憾。 C:滕子京请欧阳修作《偃虹堤记》，是为了记载岳州面貌的改变和百姓安居乐业的情景。 D:《偃虹堤记》是一篇应邀之作，欧阳修在文中借赞美滕侯表达了心中理想的为官之道。

目前PC机中使用的外存储器主要是硬盘，以下是有关硬盘的叙述：
Ⅰ．存取硬盘上的数据需要使用柱面号、磁道号和扇区号3个参数来定位
Ⅱ．平均等待时间与磁盘的转速有关
Ⅲ．内部数据传输率与磁盘的转速有关
Ⅳ．外部数据传输率与硬盘接口性能及Cache容量大小有关
上述叙述中，正确的是（）

A:仅Ⅰ、Ⅱ和Ⅲ  B:仅Ⅱ和Ⅲ  C:仅Ⅱ、Ⅲ和Ⅳ  D:全部

硬盘是PC机中主要的辅助存储器，以下是有关PC机硬盘的叙述 Ⅰ．PC机使用的硬盘接口大多是IDE（E-IDE）接口 Ⅱ．硬盘上的记录块要用柱面号、磁头号、扇区号和记录块号四个参数来定位 Ⅲ．每个扇区的容量为512字节 Ⅳ．平均寻道时间与磁盘的转速有关 以上叙述中，哪些是正确的？（）

A:仅Ⅰ、Ⅱ和Ⅲ  B:仅Ⅰ和Ⅲ  C:仅Ⅱ和Ⅲ  D:仅Ⅱ和Ⅳ

下列关于变动成本法和完全成本法的说法中，正确的有(    )。

A:按照变动成本法计算的单位成本总是低于按照完全成本法计算的单位成本 B:按照变动成本法计算的利润总是低于按照完全成本法计算的利润 C:按照变动成本法计算的利润与销量变化同向 D:按照变动成本法计算便于分清各部门经济责任，有利于进行成本控制和业绩评价