I think this may have been mentioned some time before. Basically, I think that being able to peek at the English is a way to recall what a word is before even looking at the Chinese character. This is essentially cheating, and totally comprimises the whole exercise.
I realize some people will disagree, but I think a good number of people would also agree. So, I think there should be an option for this, just as there is one for hiding pinyin when practicing writing.