Consider the following table:

$\backslash$table$[[$attribute $1,$attribute $2,$attribute $3,$attribute $4],[1,$A$,132,001],[2,$R$,143,002],[2,$A$,132,004],[1,$T$,132,$null$]]$

Which of the following pair of attributes could be a primary key for the table?

a$.$ attribute $1,$ attribute $2$

b$.$ attribute $1,$ attribute $4$

c$.$ attribute $3,$ attribute $4$

d$.$ attribute $2,$ attribute $3$