Step 1 : Introduction to the question "Which of the following is equal to one century?"
...A score is an old-fashioned unit of measurement equal to 20 years. Therefore, five score years equals 100 years, the length of one century. While the term is rarely used today, it remains familiar from Abraham Lincoln's famous Gettysburg Address, which begins, "Four score and seven years ago," referring to 87 years before the speech. The word score was once commonly used throughout the English-speaking world to count groups of twenty years or other items, although it has largely disappeared from everyday speech in modern English usage.