(a)(ab′−a′b)x+(bc′−cb′)y+(ad′−a′d)=0(b)(ab′−a′b)x+(bc′−b′c)y+(ac′−a′c)z=0(c)(ab′−a′b)y+(bc′−b′c)z+(ad′−a′d)=0(d)noneofthese.