Hello NoAgenda, It is obvious why not D:a couple of ,because there are simply more than 2 opinions about this issue. It is not also B: a plenty of ,because you can't say ' a plenty', since 'plenty' is a plural concept ,but you could say 'plenty of' and it would be correct. C: ' a great deal of ' refers also to the existence of a lot of opinions ,but is not adequately used with the word 'opinion' here.

Answer is A because the word "range" is singular "There is is a wide range of opinions on the controversial issue about cloning."