Tens of millions of Internet users make       most of the half-price promotion and it is    good opportunity for online shopkeepers to get their names known.

A．a; the

B．/; the

C．the; /

D．the; a

视网膜中央动脉阻塞的临床特征是（）

A.一眼突然发生无痛性完全失明

B.常见视网膜出血

C.樱桃红斑

D.视网膜动脉变细

E.视网膜混浊水肿