2 . Be cautious of Friday the 13th!Many people think the day is unlucky. 1 (fortune), there's only one Friday the 13th this year. As the legend goes,you should try not 2 (break)any mirrors,walk under a ladder,or even spill any salt. Why?Researchers say 3 is tough to find out how the tradition came into being. Many believe it has 4 (religion)origins. In the Christian faith,there were 13 guests at table for the Last Supper,which was held the day before the Friday 5 Jesus died. Now,Friday the 13h has become a cultural wonder. Many Americans avoid the number 13 all together, 6 (include)hotel rooms and airplane seat assignments. It even costs couples less to get married on the day. There are many other 7 (explain)behind the luckless day. Simon Bronner,a professor of American studies at Pennsylvania State. University, 8 (believe)Friday the 13h is a way for people to pin their bad luck to a certain cause:. The fact should be 9 there's nothing special about the number itself. After all,the number 13 10 (consider)to be lucky in some countries,like Italy