重點講解：
1. leave behind 留下；余留；
The criminal didn't leave behind any traces of his crime.
罪犯沒有留下任何作案的痕跡!Vd7QE+UIw!Z6d5GS。
2. at the expense of 以犧牲…的利益為代價；
But skeptics worry that costs may be trimmed at the expense of the patient.
但是持懷疑態度的人擔心費用的削減會以犧牲病人的利益為代價t2nS)D|jhY。
3. take over 接管，控制；
A British newspaper says British Airways plan to take over Trans World Airways.
一家英國報紙稱，英國航空公司計劃接管環球航空公司[AHMOOi9I+Q-Uw.(BF。
4. prop up 支撐；維持；
Investments in the U.S. money market have propped up the American dollar.
對美國資金市場的投資扶持了美元F)I@HymEREixuT=。