测定某水样的碱度时,用酚酞和甲基橙作指示剂滴定时,耗用酸液量相等。可判断该水样中含有

题型:填空题

问题:

测定某水样的碱度时,用酚酞和甲基橙作指示剂滴定时,耗用酸液量相等。可判断该水样中含有()碱性离子。

考点:锅炉水处理工锅炉水处理工题库
题型:填空题

若存在实数x∈[2,4],使x2-2x+5-m<0成立,则m的取值范围为

A.(13,+∞)

B.(5,+∞)

C.(4,+∞)

D.(-∞,13)

题型:填空题

阅读理解。

     For better eyesight, doctors advise limiting the hours of screen time and encourage having enough eye

resting time.

     However, another study shows that sitting in front of computer or TV screens for long hours is not the

only reason for myopia (近视). An Australian research team studied young children in Sydney and

Singapore to find the reasons for myopia.

     The research team found that the prevalence (流行) of myopia among children in Sydney was lower

than children in Singapore, even though they spent more time in front of computer and TV screens. The

major finding is that children in Sydney spend longer hours on outdoor activities than those in Singapore.

Indoor and outdoor sports activities both make the eyes focus on more distant objects, which prevents

the eyes from changing shape. But outdoor activities may better help avoid myopia than indoor sports

activities.

     Jane Gwiazda, who does research in sight problems, says: "Natural light is good for eye growth. And

extra vitamin D from the sun might contribute to eye growth."

     Many doctors suggest that every child get its first eye test done when he/she is about two and half

years old, and even if his/her sight seems perfect.

     It is necessary for myopic children to wear glasses to prevent headaches, trouble reading or injuries. It

is also important that schools invite doctors to test their students' eyes.

     If that is not possible, school teachers should at least encourage parents and children to have regular

eye examinations and wear glasses. And parents should remember not only to limit the total screen time

for their children, but also to encourage them to spend time outdoors.

1. What's the aim of the study by the Australian research team ?

A. To find the reasons for myopia.

B. To find the ways to treat myopia.

C. To prove the bad effects of myopia.

D. To prove the prevalence of myopia.

2. Why are there fewer children with myopia in Sydney than in Singapore ?

A. Because Sydney children watch less TV.

B. Because Sydney children have more eye resting time.

C. Because Sydney children use computers less.

D. Because Sydney children do more outdoor sports.

3. What conclusion can we draw from the passage ?

A. Sydney children don't study hard.

B. Singapore children do few exercises.

C. Outdoor activities do more good to eyes.

D. Room light does harm to children's eyes.

4. Which of the following statements is TRUE ?

A. Children should have eye tests as soon as they reach school age.

B. Doing outdoor activities with no glasses is good for myopia children.

C. Focusing on distant objects can help the eyes keep their original shape.

D. Children should limit their time in the sun in order to protect their eyes.

题型:填空题

阅读下表内容判断:

以下表述是从上表信息中得出的,请在括号内划“√”;违背了上表信息所表达的意思的,请在括号内划“×”;是上表信息没有涉及的,请在括号内划“○”。

(1)象形文字的产生比楔形文字晚500 年左右。[ ]

(2)古埃及人将象形文字刻写在泥版上记事。[ ]

(3)楔形文字因笔画独特,形状像楔子一样而得名。[ ]

(4)公元前后,楔形文字被其他文字取代,逐渐被人遗忘。[ ]

(5)象形文字和楔形文字古朴而奇妙,凝聚着古代人类的智慧。[ ]

题型:填空题

下列有关费用偏差的计算公式中,正确的是( )。

A.费用偏差=已完工程预算费用-已完工程实际费用

B.费用偏差=市场价-计划费用

C.费用偏差=实际值-预算费用

D.费用偏差=未完工程实际费用-未完工程计划费用

题型:填空题

空调器(冷气机)中之“泵头”的正确名称是()

A.制冷压缩机

B.风泵

C.水泵

D.以上皆是

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