A. into research to attempt to create the coveted blue rose, which many observers
believe would be more profitable than those previously genetically engineered---
Those has no referent. Those could refer to blue rose that was previously genetically engineered. I think there is ambiguity in the sentence. B. into research for attempting to create a flower many observers believe would
be more profitable than any previous genetically-engineered flower, the blue rose---
Incorrect modifier. The blue rose is not the previous genetically-engineered flower.C. for research for the blue rose, which many observers believe would be more
profitable than any previous genetically-engineered flower. ----
Missing attempt to create. Change of meaning. D. in research for attempting to create the coveted blue rose, which many observers
believe would be more profitable than any that was previously genetically engineered----
for attempting, I feel does not sound correct compared with 'to attempt'. Also wordy when it says would be more profitable than any that was.... E. in research to attempt to create the coveted blue rose, which many observers believe
would be more profitable than any previous genetically-engineered flower---
Correct.