Answer :
The statement that I believe is the least likely to convince an audience of acupuncture's safety is "B) Still, complications have resulted from inadequate sterilization of needles and from improper delivery of treatments." since it speaks of the complications generated by said practice without acknowledging that this happens in a rather small number, instead of focusing on delivering a positive message about acupuncture.
Statement "D) The acupuncture technique that has been most studied scientifically involves penetrating the skin with thin, solid, metallic needles that are manipulated by the hands or by electrical stimulation." can also be discouraging as many people fear needles and electricity.