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));","ALTER TABLE commercials CHANGE (description CHAR2(1000));","ALTER TABLE commercials CHANGE (description VARCHAR2(1000));","ALTER TABLE commercials MODIFY (description VARCHAR2(1000));","You cannot increase the size of a column if the table has rows."]
下列花卉中不属于块茎类的是（）。 ["马蹄莲","大丽花","花叶芋","大岩桐"]
下列何为三环类抗抑郁剂（） ["丙咪嗪","帕罗西汀","阿普唑仑","忆梦返","氟西汀"]
汽车牵引支承参数的评价指标是（）、（）和（）。
患者小张，男性，25岁，汽车司机，因继发性腹膜炎急诊手术。术后胃肠减压，如果出现下列哪种情况应停止胃肠减压（） ["减压液为食物残渣","减压液为淡黄色","减压液为棕褐色","减压液为鲜红色血液","减压液为鲜绿色"]
哪些行为属于侵犯商业秘密的不正当竞争行为？
