四、单词拼写（共10小题；每小题1分，满分10分）
根据下列句子及所给汉语注释或单词首字母，在句子右边的横线上，写出空缺处各单词的正确形式。（每空只写一词）
71、There were so many people that the company put on________（额外的）buses.
72、He will never_________（获得）anything if he doesn't work hard.
73、On _______（平均），people who don’t smoke are healthier than people who do.
74. 、He ______（按下）the button and the doorbell rang.
