“It has often been the very creations intended to save time that have been most responsible for increasing the workload. Recent research indicates that farm wives in the 1920s, who were without electricity, spent significantly less time on housework than did suburban women, with all their modern machinery, in the latter half of the century. ...”
I understand the first sentence above is a cleft sentence and followings are allowed in ‘It be’ position; It is(was), occasionally, It might be, It must have been, It may have been, It could have been, etc. However, this is the first time to me that I’ve seen ‘has often been’. Does this also have no problem in that position grammatically?
Would hope to hear your valuable opinions.