皮皮学，免费搜题
登录
搜题
【单选题】
若随机向量（X，Y）服从二维正态分布，则 ①X，Y一定相互独立； ②若P XY =0，则X，Y一定相互独立； ③X和Y都服从一维正态分布； ④若X，Y相互独立，则Cov（X，Y）=0。 几种说法中正确的是（）
A.
①②③④
B.
②③④
C.
①③④
D.
①②④
拍照语音搜题，微信中搜索"皮皮学"使用
参考答案：
参考解析：
知识点：
.
..
皮皮学刷刷变学霸
举一反三
【多选题】在进行()操作时应佩戴有深色镜片的头盔或护目镜
A.
保护焊
B.
等离子切割
C.
氧乙炔焊
D.
磨削或切削
查看完整题目与答案
【简答题】horizontal lathes, vertical lathes, turret lathes, copying lathes, automatic lathes, CNC lathes and variety of special purpose lathes
查看完整题目与答案
【单选题】在进行拆除维修塞操作时,应佩戴()进行保护。
A.
高压防护套装
B.
防护手套
C.
绝缘手套
D.
护目镜
查看完整题目与答案
【简答题】完形填空。 In a big city, everyone is in a hurry in the early morning. People are 1 the stations, buses and cars. They usually have no time for 2 . People work busily all day. At six o'clock in the evening...
查看完整题目与答案
【单选题】The English have the reputation of being very different from ail other nationalities. It is claimed that living on an island separated from the rest of Europe has much to do with it. Whatever the reas...
A.
they are geographically isolated from the European continent
B.
they have nothing to do with the other Europeans
C.
they like to keep quiet among their acquaintances
D.
they tend to be reserved by nature
查看完整题目与答案
【单选题】In the early morning all of us stood at the top of the mountain __ east of the city, watching _____burning sun rising.
A.
/; a
B.
the; a
C.
the; the
D.
/; the
查看完整题目与答案
【单选题】Ail of us would have enjoyed the party much more if there______quite such a crowd of people there.
A.
weren't
B.
hasn't been
C.
hadn't been
D.
wouldn't be
查看完整题目与答案
【简答题】—Why not go out for a walk before breakfast? —Oh,yes. _________ is my favorite time of day. A. In the early morning B. Early morning C. The early of morning D. The early morning that
查看完整题目与答案
【多选题】在进行（ ）操作时，应佩戴护目镜。
A.
使用或处理油漆
B.
使用固化剂
C.
使用溶剂
D.
手工水打磨
查看完整题目与答案
【多选题】在进行下列哪些操作时应当佩戴护目镜( )
A.
锤击
B.
钻孔
C.
磨削
D.
切削
E.
车身测量
查看完整题目与答案
相关题目：
【多选题】在进行()操作时应佩戴有深色镜片的头盔或护目镜
A.
保护焊
B.
等离子切割
C.
氧乙炔焊
D.
磨削或切削
查看完整题目与答案
【简答题】horizontal lathes, vertical lathes, turret lathes, copying lathes, automatic lathes, CNC lathes and variety of special purpose lathes
查看完整题目与答案
【单选题】在进行拆除维修塞操作时,应佩戴()进行保护。
A.
高压防护套装
B.
防护手套
C.
绝缘手套
D.
护目镜
查看完整题目与答案
【简答题】完形填空。 In a big city, everyone is in a hurry in the early morning. People are 1 the stations, buses and cars. They usually have no time for 2 . People work busily all day. At six o'clock in the evening...
查看完整题目与答案
【单选题】The English have the reputation of being very different from ail other nationalities. It is claimed that living on an island separated from the rest of Europe has much to do with it. Whatever the reas...
A.
they are geographically isolated from the European continent
B.
they have nothing to do with the other Europeans
C.
they like to keep quiet among their acquaintances
D.
they tend to be reserved by nature
查看完整题目与答案
【单选题】In the early morning all of us stood at the top of the mountain __ east of the city, watching _____burning sun rising.
A.
/; a
B.
the; a
C.
the; the
D.
/; the
查看完整题目与答案
【单选题】Ail of us would have enjoyed the party much more if there______quite such a crowd of people there.
A.
weren't
B.
hasn't been
C.
hadn't been
D.
wouldn't be
查看完整题目与答案
【简答题】—Why not go out for a walk before breakfast? —Oh,yes. _________ is my favorite time of day. A. In the early morning B. Early morning C. The early of morning D. The early morning that
查看完整题目与答案
【多选题】在进行（ ）操作时，应佩戴护目镜。
A.
使用或处理油漆
B.
使用固化剂
C.
使用溶剂
D.
手工水打磨
查看完整题目与答案
【多选题】在进行下列哪些操作时应当佩戴护目镜( )
A.
锤击
B.
钻孔
C.
磨削
D.
切削
E.
车身测量
查看完整题目与答案