The problem is difficult ________.3Q

The problem is difficult ________.3Q the problem is difficult ___ . The problem is difficult ______. This math problem is so difficult that only ________ student The problem is very difficult to ( ) The problem is () difficult for us() That problem is the most difficult ---- all the boy is c____ by the difficult problem. The problem is difficult ,but he worked it out____. The maths problem is difficult,but f___we work it out. He is busy to work out the difficult problem. 改错 The maths problem is too difficult.math为什么加s