【单选题】A ( ) is a set of attributes in a referencing relation, such that for each tuple in the referencing relation, the values of the foreign key attributes are guaranteed to occur as the primary key valu...
【单选题】利用物理或化学的方法对天然药物所含有的主要化学成分或有效成分进行定性和定量分析,用以鉴定天然药物真伪和优劣的方法是( )
【简答题】含有天然蜂蜜60%,人造蜜40%的混合蜜
【简答题】含有天然蜂蜜60%,人造蜜40%的混合蜜_____________。
【简答题】当SOP为真时,S与P的外延关系不可能有( ) A .全同关系 B.真包含于关系 C.真包含关系 D.交叉关系 E.全异关系A.B.C.D.E. E
【单选题】Each of the students, working hard at his lessons,__________to go to key universities.
【单选题】How is finding a birth mother like getting a key to a diary?
A.
A diary comes with each birth certificate.
B.
The adoptees will have a chance to find out about their mother's life.
C.
If the key opens the diary, you get a birth certificate.
D.
The adoptee will have to keep a diary before they get a birth certificate.