Possible Duplicate:
Past simple and present perfect
The first line in my research is the following:
Since the May 6, 2010 ``Flash Crash’’ event, the following question has been raised several times: Does High-Frequency Trading increase the likelihood of long tail and chaotic events in financial markets?
Should I say
Since the May 6, 2010 ``Flash Crash’’ event, the following question was raised several times: Does High-Frequency Trading increase the likelihood of long tail and chaotic events in financial markets?
I have been told that I have to avoid "has been" and even "was" in academic journals. Is there a better way for me to improve my sentence?