短语学习：

1.back and forth: 反复地，来回地

eg. Switching between these states allows Grier to move objects back and forth.
格里尔通过转换这些状态来实现向前和向后移动物体。

eg. Negotiating is the process of communicating back and forth for the purpose of reaching an agreement.
谈判是为了达成协议而反复交流的过程。 它包括说服和妥 协。

eg. The pendulum swings back and forth.
这就像单摆一样来回摆动。

2.big time: 巨大成功；大范围地；愉快的时光；第一流

eg. I owe you big time.
我欠你一个大人情。

eg. This was the magical moment, his entrance into the big time.
这是一个创造奇迹的时刻，是他走向大成功的开端。

eg. When the pressure in the big time got to be too much, the guy simply returned.
当来自上面的压力太大时，这家伙干脆甩手不干了。

2.used to: 过去常常

eg. I'm not used to getting up early.
我不习惯很早起床。

eg. You will soon become/get used to the weather here.
你很快就会习惯这里的气候。

eg. I used to do business with him.
我过去和他常有业务往来。

3.better off: 情况更好

eg. We have to do that now, because it will actually make our businesses and our families better off.
我们现在得行动了，因为那样事实上会让我们的企业和家庭更美好。

eg. If your income doubles but the prices of the goods you consume also doubles, you are no better off.
如果你的收入翻番，但所消费商品的价格也翻番，你就没有变得更富裕。