听力原文： Iran has lifted its ban on visits to a nuclear facility by U.N. experts and now will allow them to inspect the site, the International Atomic Energy Agency said Friday. It also said Tehran was ready to answer key questions on past suspicious experiments that the international community fears could be linked to a weapons pro- gram. Years of Iranian stonewalling have left the IAEA unable to ascertain whether Tehran is telling the truth in asserting that it has no nuclear weapons ambitions and that its atomic activities are meant strictly to generate power. Its refusal to cooperate with the agency was the trigger that prompted U.N. Security Council involvement last year that led to two sets of sanctions. The news item is about Iran's______.