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问题 单项选择题

通过改变pH值从而使与离子交换剂结合的各个组分被洗脱下来，可使用（）

A.阳离子交换剂一般是pH值从低到高洗脱

B.阳离子交换剂一般是pH值从高到低洗脱

C.阴离子交换剂一般是pH值从低到高

D.以上都不对

答案

参考答案：A

单项选择题

双硫腙溶于有机烃类的衍生物中，如氯仿、四氯化碳等，指出双硫腙在氯仿中的溶解度为下列何值（）。

A.0.3g/L（淡绿色）

B.0.4g/L（绿色）

C.0.64g/L（绿色）

D.1.64g/L（暗绿色）

E.17.8g/L（兰绿色）
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单项选择题

Like many other aspects of the computer age, Yahoo began as an idea, (1) into a hobby and lately has (2) into a full-time passion. The two developers of Yahoo, David Filo and Jerry Yang, Ph. D candidates (3) Electrical Engineering at Stanford University, started their guide in April 1994 as a way to keep (4) of their personal interest on the Internet. Before long they (5) that their homebrewed lists were becoming too long and (6) . Gradually they began to spend more and more time on Yahoo.

During 1994, they (7) yahoo into a customized database designed to (8) the needs of the thousands of users (9) began to use the service through the closely (10) Internet community. They developed customized software to help them (11) locate, identify and edit material (12) on the Internet. The name Yahoo is (13) to stand for "Yet Another Hierarchical Officious Orale", but Filo and Yang insist they selected the (14) because they considered themselves yahoos. Yahoo itself first (15) on Yang’s workstation, "akebono", while the search engine was (16) on Filo’s computer, "Konishiki".

In early 1995 Marc Andersen, co-founder of Netscape Communication in Mountain View, California, invited Filo and Yang to move their files (17) to larger computers (18) at Netscape. As a result Stanford’s computer network returned to (19) , and both parties benefited. Today, Yahoo (20) organized information on tens of thousands of computers linked to the web.

4（）

A.touch

B.contact

C.track

D.record
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