1. average out to 平均为
World population can be stable only if fertility rates around the world
average out to 2.1 children per woman. (31KB)
只有世界范围内的出生率能达到平均每位妇女生育2.1个子女，世界人口才可能稳定。
2. fall into 属于
Student organizations at Harvard can
fall into more than ten categories.
哈佛大学的学生社团有十余种。
3. it doesn't hurt that ……是一个优势
It doesn’t hurt to have money when you want to run for office.
要想参加竞选，经济实力就是一个优势。
4. ups and downs 沉浮
He faces the
ups and downs of his life with courage.
他勇敢地面对人生的跌宕起伏。
