【单选题】A humorous piece of writing can make the reader's emotional responses untrustworthy because ______.
A.
it expresses the truth of the sadness of human life with a sparkling surface
B.
everyone has his happy moments and unhappy moments
C.
there is an obvious line between laughing and crying
D.
it is like poetry, very rhythmic
【简答题】根据某些条件对一个关系作水平分解,选择符合条件的元组组成一个新的关系,这样的操作称为( )。 A)投影 B)选择 C)等值连接 D)自然连接
【简答题】根据某些条件对一个关系作水平分解,选择符合条件的元组组成一个新的关系,这样的操作称为( )。 A)投影 B)选择 C)等值连接 D)自然连接
【单选题】根据某些条件对一个关系作水平分解,选择符合条件的元组组成一个新的关系,这样的操作称为
【单选题】— I like speaking better than listening in English learning. —Oh, really? I think you should be good at of them.
【单选题】–I am twelve and I like English. -- Oh, really? I am twelve and I like English.
【单选题】根据某些条件对一个关系作水平分解,选择符合条件的元组组成一个新的关系,这样的操作系称为