听力原文： The authorities in Iraq say they've shut down the country's biggest oil refinery after death threat to tanker drivers. They stopped work earlier this month after receiving threatening letters. An Oil Ministry spokesman said the threats coincided with the announcement of fuel price rises. Near the town of Baiji, the refinery is one of the most important in Iraq. Threats began arriving by letter to the plant's drivers on the 21st of December. Four days later, hundreds of drivers had stopped working because of safety concerns and the refinery ceased production. The stoppage would cause fuel shortages and electricity problems as far as Baghdad and across the north. Even before the latest incident, Iraqis had become accustomed to waiting hours to fill their tanks and to daily power cuts. The Oil Ministry says it's developing a plan with the Defence and Interior Ministries to protect routes of fuel distribution. The refinery plans to reopen within the next few days. What measure are the Iraqi authorities going to take?