... 17A 18D 19C 20 B 21 A 22 A 23 C 24 D 25 D 26 B 27 C 28 A 29 C 30B 31D 32A 33B 34A 35B 36C 37A 38C 39D 40B 41A 42D 43B 44C 45B 46C 47D 48C 49D 50A 51A 52D 53A 54B 55C 56A 57A 58D 59C 60B 61C 62D 63D 64C 65 ... Viet Nam (e.g Tet holiday, Mid- Autumn Festival, National Independence Day, Teacher’s Day, Women’s Day, etc.) THE END KEY 1B 2A 3C 4C 5A 6C 7B 8C 9D 10C 11C 12D 13C 14B 15C 16A 17A 18D 19C 20 B ... the past 25 0 million years have tended to be more intense every 26 million years The periodic extinction might be due to intersection of the earth‟s orbit with a cloud of comets, but this theory...