难题

• As a last resort, there is a trick to solve some difficult problems .
  万不得已时有个诀窍可以用于解决难题。
• How to improve the quality of products was a difficult problem to him .
  如何提高产品质量对他来说可是个难题。
• I walked home in a distracted state, with my two perplexities .
  我带着这两个棘手的难题，心神不定地走回家去。
• The sudden drop in share prices has set the government a tricky problem .
  股票价格突然下跌给政府出了一个难题。
• The first difficulty was to decide what form the message should take .
  第一个要解决的难题是这消息用什么形式来表达。
• Most third world nations share a common set of economic and social dilemmas .
  大多数第三世界国家都存在一些共同的经济和社会难题。
• They are good exercise for those who like to wrestle with challenging questions .
  对于爱钻研难题的人来说，这些问题倒是很好的练习。
• Segregation of fatty material is a serious problem in anaerobic sludge digestion units .
  厌氧污泥消化单元中脂肪物质的分离是个难题。
• The presence of water containing hard particles presents a difficult problem for the sealing .
  含有坚硬颗粒的水，给密封带来一个难题。
• Ordinary people such as you and i have wrestled with these puzzles over the centuries .
  你我这样的普通人，多少年来都为这些难题伤脑筋。