第九单元
1.常考单词：
classify approximate proportion appreciation acknowledge alter lengthen wealthy neglect expectation
2. 常考词组：
to approximate to resistance to to cope with attribute … to
3. 常考句子：
1） nation classified as “aged” when they have 7percent of more of their people aged 65 or above. （para.1）
2） the nearer a society approximates to zero population growth，the older its population is likely to be - at least，for any future that concerns us now.
3） the older you are now，of course，the greater this proportion will be，and greater still if you are a woman.
4） if you are now in your thirties，you ought to be aware that you can expect to live nearly one third of the rest of your life after the age of 60.