下列最易引起阿-斯综合征的情况是（）。

A.心房扑动伴2：1传导

B.阵发性室上性心动过速

C.非阵发性室性心动过速

D.三度房室传导阻滞

E.窦性心动过速

In just three years, the Net has gone from a playground for the local people to a vast communications and trading center where millions swap information or do deals around the world.

A．business

B．shopping

C．chatting

D．meeting