Figure shows three cases: in all case the circular part has radius r and straight ones are infinitely long. For the same current the ratio of field B at centre P in the three case `B_1:B_2:B_3` is

Options

A. `(-(pi)/(2)):(pi)/(2):[(3pi)/(4)-(1)/(2)]`
B. `(-(pi)/(2)+):[(pi)/(2)+1]:[(3pi)/(4)+(1)/(2)]`
C. `-(pi)/(2):(pi)/(2):(3pi)/(4)`
D. `(-(pi)/(2)-1):[(pi)/(4)-(1)/(4)]:[(3pi)/(4)+(1)/(2)]`

Answer

A