27. the explanation for this problem involves many factors. for one thins, ______________. for another, ______________. still ______________.
        28. the causes for ______________ are varied. they include ______________. perhaps the main cause is ______________.
        29. the eventual result it brings out is ______________. and perhaps the most obvious result of ______________ is ______________.
        30. however, just like everything has both its good and bad sides, ______________ also has its own disadvantages, such as, ______________. besides, ______________.
        31. ______________ will bring the society many benefits. for one thing, ______________. for another thing, ______________.
        32. why ______________? some ______________. and the most common case is that ______________. the notable example is to ______________.
        33. there are many reasons responsible for this instance, and the following are the typical ones. for one thing, ______________, in addition, ______________. the main reason is that ______________.
        34. people had figured out many ways to solve this problem. firstly ______________. though this method has its good sides like it can ______________. one of its bad sides it brings about is that it can ______________.
        35. some reasons can explain the trend. first, ______________. second, ______________. third, ______________.