When they use "il" for the article (il mais), then you can just say "mais" as a noun. USUALLY when they say like "LO mais" that's when you have to say "THE corn." At least I believe that's how that works. I am not sure if mais can be used with the article "LO" or just "IL". But good luck on your learning! Also, for double the practice, I also use the free language site livemocha.com. I actually started out using that site, and then I found this one. I learned most beginning Italian on livemocha. so this is kind of easy for me. (only the beginning stuff)
Lo is only used for words that start with a z, an x, gn, ps or an impure s (sp, st etc.). So, you can't use lo for mais or any other 'il' word.
It can be translated to the boy has the corn or the boy has corn either are accepted in this way. However usually it doesn't work vice versa
mais = sweetcorn in british english. but it marked me down for it!
"Il" and "un" sound almost the same on the audio. That's been an issue for me on a number of audio questions
The "had" sounds more like "e' " even when slowed down. I was really confused when I thought it said "Il ragazzo e' il mais."