给水泵的出口和进口压力分别为17.65MPa和0.75MPa，取给水的平均

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问题单项选择题

给水泵的出口和进口压力分别为17.65MPa和0.75MPa，取给水的平均比容为0.001lm³/kg，给水泵效率取0.75，则给水泵的焓升为（）kJ/kg。

A．23.6

B．20.68

C．25.2

D．24.79

答案

参考答案：D

解析：

给水泵的焓升由公式

读图填空题

下图表示现代生物学关于内环境稳态调节的内容，图中数字表示生理过程或相关物质。据图分析回答：

(1)为研究胰腺分泌活动的调节机制，科学家做了下列实验：

①．刺激通向胰腺的神经，胰液分泌增多，该过程属于__________调节。

②．用盐酸注入小肠肠腔，胰液分泌增多，沃泰默认为是盐酸刺激小肠相关的神经后起调节作用，若该观点成立，图示中数字④和___________可表示该过程。

③．斯他林和贝利斯用离体的小肠黏膜加盐酸混合研磨后，将提取液注入间一只狗的静脉，狗胰液分泌也增多，证明了盐酸能使小肠黏膜产生一种化学物质，该物质能促进胰液分泌，图示中数字______表示该过程调节。该实验的对照实验做法是：将_______直接注射入小狗的血液，观察小狗胰液分泌是否增多。

(2)环境中的病原体若进入内环境，引起机体的特异性免疫，免疫系统向内环境释放有生物活性的物质③，以抑制病原体，③代表________等物质。

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Between school, homework, sports, your afterschool job, and hanging out with friends, it may

feel like there's no time for healthy eating. And when you do stop to eat, it's probably tempting to

go the quick and easy route by grabbing a burger and fries, potato chips, or candy.

Even if you take time to eat three meals a day, you may still feel hungry at times. This is

natural-during teens, a person's body demands more nutrients to grow. What's the answer? Healthy

snacks. Snacking on nutritious food can keep your energy level high and your mind alert without

taking up a lot of your time. Snacks are a great way to satisfy that hunger and get all the vitamins

and nutrients your body needs.

But you need to pay attention to what you eat. Filling your face with a large order of fries after

class may give you a temporary help, but a snack high in fat and calories will only slow you down

in the long run.

To keep energy levels going-and avoid weight gain-keep clear of foods with lots of simple

carbohydrates (sugars) like candy bars or soda. Look for foods that contain complex carbohydrates

like wholegrain breads and cereals and combine them with proteinrich snacks such as peanut butter

or lowfat yogurt (酸奶) or cheese.

Choosing healthy snacks means shopping smart. Be careful of the health claims on food packages.

Just because something is "all natural" or "pure" doesn't necessarily mean that it's nutritious. For

example, "all natural" juice drinks or sodas can be filled with sugar (which is, after all, a natural

ingredient) but all that sugar means they'll be high in calories and give you little nutrition.

A granola (麦片) bar is a good example of a snack that people think is healthy. Although granola

bars can be a good source of certain vitamins and nutrients, many also contain a great deal of fat,

including a particularly harmful type of fat called trans fat (反式脂肪酸). Check the Nutrition Facts

label on the package to be sure.

1. People think that granola bar is healthy because ________.

A. it is a good source of calories

B. it provides trans fat

C. it contains some vitamins

D. it is natural

2. In choosing healthy snacks, we should try to make sure that ________.

A. they are all natural or pure

B. they are high in nutrition

C. their packages are good

D. they contain harmless fat

3. Teens need snacks to ________.

A. keep a good figure

B. gain weight

C. help grow

D. keep healthy

4. According to the passage, all the following snacks are good EXCEPT ________.

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