Definition: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Input: A recent outbreak of E. coli linked to Chipotle restaurants in nine U.S. states has caused sales to plummet by as much as 22 percent in recent weeks, the restaurant chain announced on Friday. The Denver-based chain said sales trends have been 'extremely volatile' since it closed restaurants in Oregon and Washington in early November as a result of the outbreak. Earlier on Friday, the Centers for Disease Control and Prevention said the outbreak had expanded to nine states, with a total of 52 reported illnesses. That was up from the six states and 45 illnesses as of late November.Sales have dived by 22 percent in recent weeks as E. coli outbreak expands52 people in nine U.S. states have gotten sick from eating at Chipotle restaurantsE. coli bacteria cause diarrhea and abdominal pains, according to the Centers for Disease Control and Prevention 
 Question:_, which is known for touting the quality of its ingredients, also said Friday it was tightening its food standards.

Chipotle