What do you understand by the terms Primary Key and Degree of a relation in relational database ?

What do you understand by the terms Candidate Key and Cardinality of a relation in relational database ?

A relational database consists of a collection of

1. Tuples
2. Attributes
3. Relations
4. Keys

A(n) …………… in a table represents a logical relationship among a set of values.

1. Attribute
2. Key
3. Tuple
4. Entry