根据句子意思,用所给单词的适当形式填空.
71 Their parents are both teachers And_(I) are doctors.
72.You can make a_(decide) among the suggestions.
73.THe law of gravity_(discover)by Isaac Newton about 350 scars ago.
74.He lives on the__(nineteen ) floor of the building.
75.We had better eat more_(harm ) vegetables.
76____(luck）all of them were hurt in the accident.
77.1 am going to the USA to have a_(far) study.
78 The Great Wall as well as the palace museum__(attract)lots of tourists from abroad every year.
79.We should do everything we can_(protect)the environment.
80.By 5:30yesterday afternoon he_(ftnish)writing the laboratory report.