问题
                    
Thepupilshere_____allkindsofexerciseseverydayinthepastfewweeks
                            A:keptbusydoing
B:keepondoing
C:havekeptbusydoing
D:havebeenkeptbusydoing
                        
                        B:keepondoing
C:havekeptbusydoing
D:havebeenkeptbusydoing
正确答案是:
                        