we admit that there are still some problems about NMET we dont mean that it is of no us

问题补充：

we admit that there are still some problems about NMET, we don mean that it is of no use.

A. Until

B. While

C. As

D. Unless

答案：

A. Until

(答案→)B. While

C. As

D. Unless

解析：连词while的意思是“当.……的时候, 虽然”，如：While he loves his students, he is very strict with them. 虽然他爱他的学生, 可是他对他们很严格。