根据利息支付方式的不同，债券分为()。

A.付息债券

B.零息债券

C.信用债券

D.一次还本付息债券

E.贴息债券

The train is going _______ the tunnel. Then it will go ______to the center of the city.

A．through; towards

B．through; straight　

C．across; towards

D．across; straight