肾衰当GFR减少至正常的10％以下，血肌酐>70μmol／L时为（） A.氮质血症期

取少量MgO、A1₂O₃、SiO₂、Fe₂O₃的混合粉末，加入过量盐酸，充分反应后过滤，得到沉淀X和滤液Y。下列叙述正确的是[ ]

A．上述四种氧化物对应的水化物中，Al(OH)₃酸性最强

B．向沉淀X中加入氢氟酸，沉淀X不溶解

C．溶液Y中的阳离子主要是Mg²⁺、Al³⁺、Fe³⁺、H⁺

D．溶液Y中加入过量氨水，所得沉淀为Fe(OH)₃和Mg(OH)₂

A quick look at an e-reader

New, High-Contrast（高对比度） E-Ink Screen

50% better contrast than any other e-reader. The clearest text and sharpest images.

Read in Bright Sunlight

Unlike LCD screens, its screen reads like real paper, with no glare. Read as easily in bright sunlight as in your living room.

Lighter Than a Paperback

Weighing only 8.5 ounces and 1/3 of an inch thick, it is lighter than a paperback and thinner than a magazine.

Holds 3,500 Books

We doubled its storage so you can carry up to 3,500 books.

Battery Life of Up to One Month

A single charge lasts up to one month with wireless off. Keeping wireless always on, it can go for up to three weeks without recharging.  

Books in 60 Seconds

With fast, free wireless delivery, you can start reading books in less than 60 seconds. No computer required.

______

Over 670,000 books, including 107 of 111 New York Times Best Sellers, plus audiobooks, periodicals and blogs. For non-U.S. customers, content availability varies.

Free, Out-of-Copyright Books

Over 1.8 million free, out-of-copyright, pre-1923 books are available such as Pride and Prejudice.

Low Book Prices

Over 550,000 books are $9.99 or less, including 73 New York Times Best Sellers of the present time.

Free Book Samples (样品)

Download and read first chapters for free before you decide to buy.

小题1:If you want to use the e-reader longer, you should ______.

A．charge it frequently

B．keep wireless off

C．use it in bright sunlight

D．read in a quiet room小题2:Which of the following can best fill in the blank in the text?

A．Large selection.

B．Excellent service.

C．Reasonable prices.

D．Interesting content.小题3:What is this text，mainly about?

A．What an e-reader is.

B．Who needs an e-reader.

C．How to use an e-reader.

D．The advantages of an e-reader.

金属的塑性变形会导致其（）提高（）下降，这种现象称为加工硬化.

平行滴定时，每次都应将初刻度调整至（），这样可减少滴定管刻度的系统误差或读数误差。

在合同解释中优先于其他文件的是( )。

A．双方往来函件

B．中标人投标时递交的主要技术和商务文件

C．合同价格条款

D．合同补遗或合同谈判纪要