【正文】
enty hours each day. 9. It39。s hard to say whether the plan is practicable. 10. There is no doubt that you will be helped by others if you have any difficulties. 11. It seems certain that they have made a series of experiments. 12. It is said that bats have been using radar for millions of years. 13. To tell the truth , many mistakes we made could have been avoided. 14. As we know, it was not until recently that the problem was solved. 15. It must be admitted that you haven39。t done what you promised to do. 16. In my opinion, this puter is different from that one you saw. 17. It is certain that we have a long way to go. 18. All this shows that nothing can prevent us from reaching our aims. 19. As far as we know, it took him more than a year to write the book. 20. It has been proved that every substance, no matter what it is, is made up of atoms. 21. It has been decided that we are going to build a railway whose base must be pleted within this year. 22. It is obvious (evident) that the success of the innovation depends on our concerted efforts. 23. To be frank, whether you like it or not, you have no other choice. 24. It is natural that one may have trouble expressing plicated ideas in simple English. 25. What is more important, the agreement they have negotiated is being carried out. 26. We will be successful as long as we persevere