1. average out to 平均為
World population can be stable only if fertility rates around the world average out to 2.1 children per woman. (31KB)
只有世界范圍內的出生率能達到平均每位婦女生育2.1個子女，世界人口才可能穩定hkJI82X*=jqzNkC5=J。

2. fall into 屬于
Student organizations at Harvard can fall into more than ten categories.
哈佛大學的學生社團有十余種&6*JA-=||*WvUhN6R5。

3. it doesn't hurt that ……是一個優勢
It doesn’t hurt to have money when you want to run for office.
要想參加競選，經濟實力就是一個優勢deEJFh=32X|L0|M9g。

4. ups and downs 沉浮
He faces the ups and downs of his life with courage.
他勇敢地面對人生的跌宕起伏vXveF~FByL+.GcW*24。