—How long do you suppose it is _______he arrived here？

—No more than half a week.[ ]

A. when      

B. before        

C. after      

D. since

树脂拉丝渐进镜片的边厚应不小于（）。

A、0.8-1.2mm

B、2.0-2.5mm

C、1.5-2.0mm

D、1.0-1.5mm