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酿酒酵母表达系统的优缺点?

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高锟的发明使（）在全球迅猛发展。

A. 虚拟网络
B. 光纤
C. 互联网
D. 信息高速公路

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供聚丙烯装置用界区氮气压力一般是（）MPa。

A. 0.3~0.4
B. 0.4~0.5
C. 0.5~0.8
D. 1.0以上

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RNC用户面单用户码流跟踪对应的toolkit任务类型是哪个？（）

A. RNLC_UE SIGNAL BY UEID
B. RNLU_UE SIGNAL BY UEID
C. RNLC_UE SIGNAL BY CELL ID ANDNUM
D. RNLC_IU COMON SIGNAL

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You need to change the definition of an existing table. The COMMERCIALS table needs its DESCRIPTION column changed to hold varying length characters up to 1000 bytes. The column can currently hold 500 bytes per value. The table contains 20000 rows. Which statement is valid?（）

ALTER TABLE commercials MODIFY (description CHAR2(1000));
B. ALTER TABLE commercials CHANGE (description CHAR2(1000));
C. ALTER TABLE commercials CHANGE (description VARCHAR2(1000));
D. ALTER TABLE commercials MODIFY (description VARCHAR2(1000));
E. You cannot increase the size of a column if the table has rows.

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