If A is the primary key of relation R（A,B,C), then AC is：

Which is the main idea of the passage?

A．Modern technology is the key to the improvement of standard of living.

B．The three major factors of production—land, labor and capital are all influenced by technology.

C．Technology is the response to our needs.

D．The United States is making great efforts to advance its technology.

Which is the main idea of the passage?

A．Modern technology is the key to the improvement of standard of living.

B．The three major factors of production—land, labor and capital are all influenced by technology.

C．Technology is the response to our needs.

D．The United States is making great efforts to advance its technology.

For relation R where primary key contains multiple attributes,no non-key attribute should be functionally dependent on a part of the primary key. This relation R is at least in

A． 1NF

B．2NF

C．3NF

D．BCNF

For relation R where primary key contains multiple attributes,no non-key attribute should be functionally dependent on a part of the primary key. This relation R is at least in

A． 1NF

B．2NF

C．3NF

D．BCNF

A．Primary Key NOT NULL

B．Primary Key

C．Foreign Key

D．Candidate Key

A．Primary Key NOTNULL

B．Primary Key

C．Foreign Key

D．Candidate Key

A．Primary Key NOTNULL

B．Primary Key

C．Foreign Key

D．Candidate Key

A．PrimaryKey，NOT NULL

B．Primary Key

C．Foreign Key

D．Candidate Key

Which of the following is the key factor in the immediate approval of Labor Day as a national holiday?

A) The lawmakers’ respect for the workers.

B) The worker’s determination to have a holiday of their own.

C) The socialists’ demands for thorough reform.

D) The politicians’ fear of the workers’ anger.