一个容量为80的样本，最大值是141，最小值是50，取组距为10，可以分成（ ）

阅读理解。

     The old man walked with a cane (拐杖) slowly into the restaurant. His poor jacket, patched(打补丁的) trousers, and worn-out shoes made him stand out from the usual Saturday morning breakfast crowd. Unforgettable were his pale blue eyes that shone like diamonds, large rosy cheeks, and thin lips held in a

steady smile.

     He walked toward a table by the window. A young waitress watched him and ran over to him, saying, "Here, Sir. Let me give you a hand with that chair."

  Without a word, he smiled and nodded a thank you. She pulled the chair away from the table.

Supporting him with one arm, she helped him move in front of the chair, and get comfortably seated.

Then she pushed the table up close to him, and leaned his cane against the table where he could reach it.

     In a soft, clear voice he said, "Thank you, Miss."

     "You are welcome, Sir." She replied. "My name is Mary. I'll be back in a moment. If you need

anything, just wave at me!"

     After he had finished a hearty meal of pancakes, bacon, and lemon tea, Mary brought him the change,

helping him up from his chair and out from behind the table. She handed him his cane, and walked with

him to the front door. Holding the door open for him, she said, "Come back and see us, Sir!"

     He nodded a thank you and said softly with a smile, "You are very kind!"

     When Mary went to clean his table, she was shocked. Under his plate she found a business card and

a note written on the napkin(餐巾纸), under which was a $100 bill.

     The note on the napkin read, "Dear Mary, I respect you very much, and you respect yourself, too. It

shows by the way you treat others. You have found the secret of happiness. Your kind gestures will shine

though those who meet you."

     The man she had served was the owner of the restaurant. This was the first time that she, or any of

his workers, had seen him in person.

1. Mary ran over to the old man because___________. 

A. the old man was the boss of the restaurant

B. She was worried that the old man might cause trouble to the restaurant

C. the old man had asked her to wait on him

D. she saw the old man had some difficulty moving and taking a seat

2. The man came to the restaurant___________.

A. to have breakfast        

B. to see his workers

C. to find out how the workers in his restaurant were working

D. to see how Mary served customers

3. The words the man left on the napkin showed that___________.  

A. Mary's kind service would bring in more money for her

B. respecting others means respecting oneself

C. serving others is a respectable job

D. Mary would get a rise as a result of her kindness

4. Which of the following titles goes best with the story?

A. Shining Kindness            

B. A Kind-hearted Girl

C. Kindness Means Chances      

D. A Waitress and Her Boss

存在职业危害的企业，应当建立健全的职业危害防治管理制度和操作规程有哪些？（任意答出三项即可）

离心泵的潜伏汽蚀发生在（）时。

A．有效汽蚀余量Δha小于必需汽蚀余量Δhr

B．Δha=Δhr

C．Δha＞Δhr，但前者接近后者

D．Δha接近临界汽蚀余量Δhc

作为商品的资本是

A．商业资本

B．借贷资本

C．产业资本

D．流通资本

通过太空科学实验，科学家发现并证实了暗能量对宇宙膨胀的加速作用，并以此测算出宇宙的实际年龄，使人类在科学揭示宇宙和生命起源及演化奥秘的道路上又向前迈进了一步。这（）

①进一步证明世界的统一性在于物质性

②说明物质世界是运动和静止相统一的

③说明实践的发展推动人类认识的发展

④说明追求终极真理是一个曲折的过程

A.①②

B.②④

C.①③

D.③④