We have no reason to think that failure to use the same research techniques was one of the factors that made it difficult for physicists to realize atoms were being split. So we have no reason to think (A) would have caused physicists to realize that atoms were being split more quickly.

This would eliminate one of the things the author identifies as causing physicists difficulty in realizing atoms were being split in the neutron bombardment experiments. That’s why we have reason to think that (B), if true, would have shortened the time required for physicists to realize that atoms were being split.

The physicists’ awareness of the calculations showing that in principle it was possible to split atoms is not described as one of the things that made it difficult for physicists to understand that the neutron bombardment experiments involved splitting atoms. So we have no reason to think (C) would have caused physicists to realize that atoms were being split more quickly.

Not having enough physicists focused on doing neutron bombardment experiments isn’t identified as one of the things that made it difficult for physicists to understand that the neutron bombardment experiments involved splitting atoms. In fact, we already had enough evidence of atom-splitting before Meitner’s insight. So we have no reason to think (D) would have caused physicists to realize that atoms were being split more quickly.

The lack of experiments involving bombardment of non-uranium substances isn’t identified as one of the things that made it difficult for physicists to understand that the neutron bombardment experiments involved splitting atoms. So we have no reason to think (E) would have caused physicists to realize that atoms were being split more quickly.