Which of the following statements best states the main idea of the passage? (A)Human cloning research can improve reproductive technology and thus help infertile couples have kids. (B)With so many possible ethical problems, we should think twice before setting up a national policy on cloning. (C)The way to prevent the abuses of cloning may hinder beneficial medical and scientific progress. (D)Human cloning research should be stopped because it is not ethically acceptable.