题目内容：
Below is a table showing the killers in every 100 deaths in a city during the last three decades. Look at the graph and write an essay of about 120 words making reference to the following points:1 ) the distribution of killers in different decades and the general trend in these decades
2 ) the possible reasons for the distribution of these killers in the city
Killers in Every 100 Deaths
| Period | Cancer | Heart disease | Traffic Accidents | Other Causes |
| 1970s | 2l | 16 | 7 | 38 |
| 1980s | 28 | 26 | 15 | 31 |
| 1990s | 27 | 27 | 21 | 25 |
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答案解析：