Which example of Java Persistence identity definitions is portable and correct assuming NO mapping descriptor is present?

Which example of Java Persistence identity definitions is portable and correct assuming NO
mapping descriptor is present?

A.
@Entity public class A {
@ld private float id;
// more code here
}

B.
@ldClass(com.acme.LineltemPK.class)
@Entity
public class Lineltem {
@ld int orderld;
@ld int lineltemld;
// more code here
}

C.
@Entity public class Project {
@ld @GeneratedValue(strategy=TABLE)
public String getProjectld() {return pid;}
// more code here
}

D.
@Entity
public class Employee {
@ld public java.util.Date getBirthday() {return bday;}
// more code here
}