(A)→(P) E=(a2+x2)23kqx
(B) →(Q),(S)
A rotating (accelerated) charge creates a magnetic field. There is also a magnetic movement, namely, m=iA associated with it. (C)→(Q),(S) 2(a2+x2)23μ0ia2 m=i0A (D)→(Q),(R),(S)
Time-varying current creates a time-varying field. Hence, the magnetic flux also varies with time, which creates induced emf (induced E ) in accordance with Faraday's law.