The story goes that two friends were walking through the desert. During some point of the journey they had an argument, and one friend slapped the other one in the face. The one who got slapped felt hurt, but without saying anything, wrote in the sand: "Today my best friend slapped me in the face." They kept on walking until they found an oasis（绿洲）, where they decided to take a bath. The one who had been slapped got stuck in the mire and started drowning, but the friend saved him. After he recovered from the near drowning, he wrote on a stone: "Today my best friend saved my life." The friend who had slapped and saved his best friend asked him, "After I hurt you, you wrote in the sand and now you write on a stone. Why?" The other friend replied: "When someone hurts us we should write it down in sand where winds of forgiveness can erase it away. But when someone does something good for us, we must engrave it in stone where no wind can ever erase it."
When Mike was walking through the town, he noticed a stranger man. The stranger looked at him with a big frown(皱眉)and it made Mike very uncomfortable. Mike did nothing w_____71___ , but the man still frowned at him. He was so angry that he frowned at the man with his tongue(舌) out. And he found most of the people around looked unhappy and frowned. Mike wondered w____72____ so many people frowned at each other. A clever idea came into Mike’s head. He should s____73____ first. It seemed silly at first, but he want to h_____74___ a try. When a woman walked towards him, he smiled a___75___ her and the lady smiled at him, and most of the people smiled at him, too. Everybody seemed happy b______76_____ of the smile of the clever boy. Then Mike once again met the stranger and the man still looked at him w____77___ a frown. Mike had a good idea. He smiled a big smile w___78___ the man passed him. The man stopped, looking at Mike’s face and he started to smile. The two strangers laughed and they b_____79_____ felt happy. Just a smile lifts you up f____80____ a feeling of down. So when you see a man with a frown, put a smile on your face. And you’ll find that the world is a happy place.