PREP2-18

Although the first pulsar, or rapidly spinning collapsed star, to be sighted was in the summer of 1967 by graduate student Jocelyn Bell, it had not been announced until February, 1968.

(A) Although the first pulsar, or rapidly spinning collapsed star, to be sighted was in the summer of 1967 by graduate student Jocelyn Bell, it had not been announced until February, 1968.

(B) Although not announced until February, 1968, in the summer of 1967 graduate student Jocelyn Bell observed the first pulsar, or rapidly spinning collapsed star, to be sighted.

(C) Although observed by graduate student Jocelyn Bell in the summer of 1967, the discovery of the first sighted pulsar, or rapidly spinning collapsed star, had not been announced before February, 1968.

(D) The first pulsar, or rapidly spinning collapsed star, to be sighted was observed in the summer of 1967 by graduate student Jocelyn Bell, but the discovery was not announced until February, 1968.

(E) The first sighted pulsar, or rapidly spinning collapsed star, was not announced until February, 1968, while it was observed in the summer of 1967 by graduate student Jocelyn Bell.

不知道to be sighted was observed 作为句子的什么成分？？C这样before的表达是不是一定不可以?还有C的过去完成时？？

答案是D吗？

The first pulsar （to be sighted定语修饰pulsar） was (谓语)observed

C的逻辑主语错误，这个是很严重很经常考到的错误

observed的主语应该是pulsar

恩，C的错误被忽略了。

但是，D中to be sighted做定语，好像哪里看到过不可以的，只有ing、ed两种形式？？？

same question not solved:C这样before的表达是不是一定不可以?