腰椎穿刺的禁忌情况是

A．Kernig征阳性

B．Babinski征阳性

C．呼吸功能严重障碍

D．中枢神经系统感染性疾病

E．脑血管疾病检查脑脊液

Scientists say it may be five or six years         it is possible to test this medicine on human patients.      

[ ]

A. since                        

B. after      

C. before                      

D. when