自然界中的氨基酸常见分类原则是( )。 A．按蛋白质来源分类 B．按营养价值分类

When she looked ahead, Florence Chadwick saw nothing but a solid wall of fog. Her body was numb(全身麻木). She had been swimming for nearly sixteen hours. Already she was the first woman to swim the English Channel in both directions. Now, at age 34, her goal was to become the first woman to swim from Catalina Island to the California coast.

On that fourth of July morning in 1952, the sea was like an ice bath and the fog was so dense she could hardly see her support boats. Sharks cruised toward her lone figure, only to be driven away by rifle shots. Against the cold sea, she struggled on ---- hour after hour ---- while millions watched on national television.

Alongside Florence in one of the boats, her mother and her trainer offered encouragement. They told her it wasn't much farther. But all she could see was fog. They urged her not to quit. She never had … until then. With only a half mile to go, she asked to be pulled out.

She told a reporter hour later, "Look, I'm not excusing myself, but if I could have seen land I might have made it." It was not tiredness or even the cold water that defeated her. It was the fog. She was unable to see her goal.

Two months later, she tried again. This time, despite the same dense fog, she swam with her goal clearly pictured in her mind. She knew that somewhere behind that fog was land and this time she made it! Florence Chadwick became the first woman to swim the Catalina Channel, eclipsing(超出) the men's record by two hours!

44. Florence Chadwick was the first woman to swim across ________.

A.the English Channel             B.the Catalina Channel  

C.the California coast              D.Catalina Island

45. Florence failed on her first trial mainly because of _______.

A. the sharks     B. the tiredness      C. the cold water     D. the bad weather

46. The underlined word “then” in this passage refers to the period when _______.

A. she had swum nearly sixteen hours           B. sharks swam toward her

C. she couldn’t see her support boats          D. millions of people watched her on TV

47. We can infer from the passage that it was ______ that resulted in her success.

A. her family’s encouragement            B. her iron will 

C. her swimming skills 　                D. the good weather

男性，19岁，2日来出现皮肤紫癜，以下肢为主，两侧对称，颜色鲜红，高出皮肤表面，伴有关节及腹痛。应诊断为（）

A.急性白血病

B.过敏性紫癜

C.血小板减少性紫癜

D.急性关节炎

E.急腹症

建筑安装工程费用构成中直接工程费不包括( )。

A．人工费

B．财产保险费

C．材料费

D．施工机械使用费

简述YJ17卷烟机吸风室与烟枪调整的技术要求。