删除数据库db_student的命令是( ) A: DELETE DATABASE db_student; B: DROP DATABASE db_student; C: DELETE db_student; D: DROP db_student;

1.创建数据库db_student

创建一个名称为db_student的数据库

【单选题】使用命令添加用户student,设置密码为student,然后使用命令删除该用户。 A. useradd student passwd student userdel student B. useradd student passwd student sudo userdel student C. useradd student sudo passwd student sudo userdel student D. su root useradd student passwd student userdel student

某拟建企业厂界与界外居民楼测点背景噪声值为55dB()、53dB(),预测投产后两处测点的噪声贡献值分别为55dB()、53dB(),厂界和居民楼处噪声预测值分别为(A)。A.58 dB(A)、56 dB(A)B.55 dB(A)、53 dB(A)C.55 dB(A)、56 dB(A)D.58 dB(A)、53 dB(A) A: 58 dB(A)、56 dB(A) B: 55 dB(A)、53 dB(A) C: 55 dB(A)、56 dB(A) D: 58 dB(A)、53 dB(A)

According to WHO the normal hearing is ______. ( ) A: 10-20 dB B: 0-20 dB C: 0-25 dB D: 10-25 dB

The sound of a band is rated as 50 dB at a distance of 30.0 m. What is the dB sound level of the band when one is 10.0 m from the band? A: 59.5 dB B: 57.3 dB C: 55.2 dB D: 52.9 dB E: 50.1 dB

大型在线式UPS 噪声（）。 A: ＜55 dB B: ＜60 dB C: ＜70 dB D: ＜80 dB

‏删除数据表student的命令是________。‏ A: drop table student; B: drop student; C: delete table student; D: drop student;

VBA中打开“student”表的语句是( )。 A: Docmd．OpenForm”student” B: Docmd．OpenQuery"student" C: Docmd．OpenTable"student" D: Docmd．Openreport"student"