The following question consists of two sets of figures 1, 2 and 3, 4 which constitute the problem-set-while figures a, b, c and d constitute the answer set. There is a definite relationship between figures 1 and 2. Establish a similar relationship between figure 3 and 4 by choosing a suitable figure 4 from the answer set.

A

a

B

b

C

c

D

d