Link to the correct answer to this question.

. com/article/53/55/59/2005-09/article _ 17272 . html

If conditions permit, students can also be guided to use ancient famous sentences. When I was doing a math problem last night, I couldn't find the correct solution despite constant thinking and repeated calculations. Dad came over and gave me some advice. I solved the problem quickly. This is really' there is no road to doubt, and there is a village in the open'! "