Answer:
Option A,B,C
Explanation:

Force on the complete wire = force on straight wire PQ carrying a current I.
F=I(PQ×B)
=I[{2(L+R)ˆi}×B]
This force is zero if B is along ˆi direction or x-direction . If magnetic field is along ˆj direction or ˆk direction,
|F|=F=(I)(2)(L+R)Bsin900
or F= 2I(L+R)B
or F∞(L+R)
∴ Options (a),(b) and (c) are correct.