Right now, lots of people search for products on the Internet but still buy them at stores. Internet shopping will really ____ when people are sure that it is safe.

A．set up

B．set off

C．take off

D．take up

下列哪项属于渐进镜的缺点（）

A.无像跳

B.中近距离视野缩小

C.配戴者需要更多的垂直转动眼位

D.视觉更接近于老视初期者

E.曲线效果