An early typewriter produced letters quickly and neatly; the typist, _____ couldn't see his work on his machine.

A．however

B．therefore

C．yet

D．although

债券票面上的基本要素不包括（）。

A.债券的票面价值

B.债券的到期期限

C.债券的票面利率

D.债券的持有人名称