1 . 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
