【答案解析】传统的美国家庭都是一个“核心家庭”。核心家庭指的是丈夫、妻子和儿女。今日美国的一般家庭有两个或三个孩子(或许还有几只宠物)。在某些文化里，家族居住在一起成为大家庭，甚至可能几代人住在一起。在美国，只有少数的情况下才会有一个以上的家庭同住一个屋檐下。 [解析]
The traditional American family is a "nuclear family" A nuclear family refers to a husband and wife and their children. The average American family today has two or three children (and maybe a few pets). In some cultures, people live close to their extended family. Several generations may even live together. In America, only in a few cases does more than one household live under one roof.

【答案解析】2000年1月1日，全球的人都在观看21世纪的第一次日出。最著名的科学杂志《自然》的名誉编辑约翰·马多克斯爵士指出，6400万年前一颗小行星曾撞击地球，导致恐龙的毁灭。“我们今天得以生存应感谢那颗小行星。它为同我们一样的哺乳动物留下了滋生繁衍的空间。” [解析]
On January 1st, 2000, humans all over the planet watched the rise of the first sun of the 21st century, Sir John Maddox, Editor Emeritus of the pre-eminent science magazine Nature, points out that it was an asteroid hitting Earth 64 million years ago that killed off the dinosaurs. "We owe our present existence to that asteroid. It made room for mammals like ourselves to flourish on Earth."