汉译英：
1.如果不是因为他的帮助，我们不可能克服重重困难
2.是我们完成工作的时候了。
3.不幸的是他们没能考虑到交通拥挤，到机场时太晚了，没能赶上那次航班。
4.你一旦定出了一个学习计划，就应该把它付诸实践。
5.他希望在周末能赶上他落掉的课程。
英译汉：
1.It is not yet known whether he will come on time.
2.What you said has nothing to do with what we are discussing.
3. No matter how great the difficulty may be, we won’t lose confidence.
4.It is reported that the building of the railway is stopped.
5.Not only is he a great scientist, but also he is quite good at music.
参考答案：
1.Had it not been for his help, we couldn't have overcome all the difficulties.
2.It is time that we finished our work.
3.Unfortunately they hadn't taken the heavy traffic into account and it was too late to catch their flight when they got to the airport
4.Once you have worked out a study plan, you should put it into practice.
5.He hopes to catch up on the lessons he missed during the weekend.
1. 他能否按时到达，现在还不得而知。
2. 你所说的与我们正在讨论的豪不相干。
3.不管困难多大,我们都不会失去信心。
4. 据报道，那条铁路停止修建了。
5. 他不仅是个伟大的科学家，而且在音乐上也颇有造诣。
