题目

He is considered ___________ the work ahead of time.   A. finishing               B. to finish                          C. having finished         D. to have finished 答案：D 解析: 略用配方法解方程：x2-4x+2=0，下列配方正确的是（ ）A．（x-2）2=2B．（x+2）2=2C．（x-2）2=-2D．（x-2）2=6