GMAT Sentence Correction (SC) | Re: Although the first pulsar, or rapidly spinning collapsed

Although the first pulsar, or rapidly spinning collapsed star, to be sighted was in the summer of 1969 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 1969 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,