In the loops shown in fig. all curved section are either semicircles or quarter circles. All the loops carry same current. The magnetic fields at the centre have magnitudes `B_1, B_2,B_3 and B_4`. Then,
A. `B_(4)` is maximum
B. `B_(3)` is minimum
C. `B_(4)gtB_(1)gtB_(2)gtB_(3)`
D. `B_(1)gtB_(4)gtB_(3)gtB_(2)`