Answer:
There is no much room here for choices in words in Spanish. The best way to answer this question is to take in the clues that we have in the sentence. Since we are talking about the movies, and popcorn, then to fill in the blank space we also need to think of different food choices that would be made out of chocolate, and that you usually find in a movie theater vendor site. Given this, there are two words that could be used: cookies and bars. Thus, the answers could be as follows:
1. No tengo hambre. Comí muchas palomitas y barras (bars) de chocolate (this is a possibility, though logically, you would not think about eating too many candy bars)
2. No tengo hambre. Comí muchas palomitas y galletas (cookies) de chocolate. (To me, this one is the one that makes the most sense, given that people tend to eat packs of cookies. Another clue is the plural in palomitas, and the fact that comí muchas... allows us to know that the word to be used in the blank has to also show coherence with the abundance of food that was eaten and that made the person not be hungry. This is also a reason why I think cookies is the best choice.)
