(1 – 3 – a); (2 – 4 – b); (3 – c); (4 – d)

(1 – 3 – c); (2 – 4 – d); (3 – a); (4 – b)

(1 – a); (2 – b); (3 – c); (4 – d)

(1 – b); (2 – a); (3 – d); (4 – c)