阅读下面短文，掌握其大意，然后从1～15各题所给的A、B、C、D四个选项中，选出最佳选项。
Some plays achieve so much success that they run for years on end.In many ways，this is __1__for the poor actors who are required to go on repeating the same __2__night after night.One would __3__them to know their parts by heart and never have cause to falter(结巴)．Yet the thing is not always the case.
