Annie Jump Cannon, ________ discovered so many stars that she was called "the census taker of the sky".

A．a leading astronomer,

B．who, as a leading astronomer,

C．was a leading astronomer,

D．a leading astronomer who

下列票据丢失之后不能挂失止付的是（）。

A.未承兑的商业汇票

B.支票

C.填明“现金”字样和代理付款人的银行汇票

D.填明“现金”字样的银行本票