重點講解：
1. come upon
偶然碰到（或發現）；
eg. I've just come upon a beautiful poem in the book.
我在這本書里偶然發現了一首優美的詩。
eg. If you're unlucky enough to come upon one of these dangerous creatures. The safest thing to do. . . Is run the other way.
如果你非常不幸地遇到一個這樣的危險生物，最安全的做法，就是擇路而逃。
2. all of a sudden
突然地；出乎意料地；
eg. All of a sudden he turned about and saw me.
他突然轉過身來看見了我。
eg. It became overcast all of a sudden.
天一下陰了下來。
3. face to face with sb.
面對面；直面；
eg. We were strolling into the town when we came face to face with Jacques DuBois.
我們信步向鎮子走去，迎面碰上雅克·杜波依斯。
eg. I found myself face to face with her in the market, so I couldn't get away.
我在市場上和她面對面碰上了，所以脫不開身了。
4. at that instant
在那個時候；在那一瞬間；
eg. At that instant the museum was plunged into total darkness.
就在那時，博物館陷入了一片漆黑。
eg. At that instant, I heard the sound of steps, followed by abrupt knocks on my door.
就在此時，我聽見樓梯響，接著是急促的敲門聲。
5. be about to do sth.
即將（做…）的；快要（發生…）的；
eg. He was about to speak. Again he bottled himself up.
他想說話又忍住了。
eg. I was just about to call you.
我正準備打電話給你。