_安徽成考网

__ is known to the world, Mark Twain was a great American writer.

• A、As

• B、Once

• C、That

• D、It

What does the underlined word "centenarians" in Paragraph 1 refer to?

• A、People who have secret lifestyles.

• B、People who enjoy physical exercise.

• C、People who are one hundred years old or older.

• D、People who carry the gene for being slim.

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