12. Though typically about two inches taller now than 140 years ago, today's people — especially those born to families who have lived in the U.S. foe many generations — apparently reached their limit in the early 1960s.
【分析】复合句。句子主干为 today's people reached their limit。句首的 though 引导让步状语;破折号之间的部分为插入语,补充说明 today's people,其中包括 who 引导的定语从句修饰。
【译文】尽管总的来说,美国人的身高比140年前高出大约二英寸,但他们——特别是那些出生于在美国生活了几代的家庭的人——其身高显然在20世纪60年代初期已达到极限,不可能再增长。
13.But as diet and health improved, children and adolescents have, on average, increased in height by about an inch and a half every years, a pattern known as the secular trend in height.
【分析】复合句。as 引导时间状语从句,主句主干为 children and adolescents have increased in height。on average 为插入语;补充说明主句,其中过去分词结构 a pattern known as...作 a pattern 的后置定语。
【译文】但是随着饮食和健康水平的提高,儿童和青少年的平均身高每20年增加大约1.5英寸,这种模式被称作“身高长期增长趋势”。
【点拨】on average 意为“平均起来,一般来说”,也可说成 on an average。该短语在句中的位置比较灵活,可以放在句首、句中和句尾。
【临摹】在全世界,美国人平均身高是最高的。