In 2009, scientists suspected that the swine flu came into the United States from Mexico, and President Obama was asked why he didn’t close the U.S. border with Mexico. “Closing the border now,” he said, “would be like closing the barn door after the horses were out. I think our healthcare system is up to the task of taking care of the sick while we combat this disease and bring it to its knees.” Americans are the key to keep the swine flu from spreading. Health officials advised that the swine flu was a raging fire that could be stopped if more Americans would keep their hands washed, cover their mouths while coughing, and stay home from work or school if they were sick.

Which of these is an example of a metaphor?
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". . .key to keep the swine flu. . ."
". . .swine flu came into. . ."
". . .the swine flu was a raging fire. . ."
. . .keep their hands washed. . ."

". . .the swine flu was a raging fire. . ." is an example of a metaphor.

(Referencing the article from the previous question) What does the President mean by the simile "like closing the barn door after the horses are out"?

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U.S. border crossings usually are housed in big buildings referred to as "barns."
The President used the simile because he knows that border gate is similar to a barn door.
Although called "swine flu," the President knows that the disease is spread by horses.
The disease has already entered the country, so closing the border won't keep it out.

The President means that closing the U.S. border with Mexico at that point would be ineffective because the swine flu had already entered the country. Just as it would be useless to close a barn door after the horses have already escaped, closing the border would not prevent the spread of the swine flu since it had already made its way into the United States.

whats the answer?

The correct answer is: The disease has already entered the country, so closing the border won't keep it out.