We shouldn't be tested on English grammar. http://i.imgur.com/Sbshy.png
The first two options are identical except for the of/off thing. I don't even need to look at the Italian sentence to see that the first option (a lot off) is wrong. In my opinion, all options should use correct English grammar. Choosing between "a lot off" and "a lot of" doesn't help improve my Italian at all. The first option should be replaced with something completely different, for instance, "We drink a lot of lemonade."