根据首字母及所给汉语注释和句子意思。
51. I can’t understand what you said. Would you please make it much s______ ?
52. At the end of the letter, he sent his best r______to my parents.
53. The rising sun is______(特别的)beautiful to look at from here.
54. He didn’t show his anger by______(控制)himself.
55. Which do you think is the greatest______(发明)in the last century?