What sentence should come second in the paragraph?

Rearrange the given four sentences (A),(B),(C),(D)  in the proper sequence so as to form meaningful paragraphs and then answer the given questions. For the hint first sentence of the given paragraph has been highlighted.                                                           
A.       The practice of taking performance boosting drugs among athletes.
B.         But checking it is not going to be easy.
C.         Is generally considered to be unfair.
D.         Of the detection technology. E.          For the user is generally one jump ahead.