1. I ate little food on my lunch plate.

2. I ate a little food on my lunch plate.
3. I ate less food than Bill.
4. Bill ate more food than me.
5. I ate the least food in my class.
6. I ate the least food of all my classmates.
7. I ate the least food of all of us.
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Are they all grammatical? Would you correct some errors?

They're all fine if you change "me" to "I" in sentence 4. (Do you know why?)

1. I ate little food on my lunch plate. - Grammatically correct, but it implies that very little food was eaten, possibly not enough.

2. I ate a little food on my lunch plate. - Grammatically correct. This implies that some small amount of food was eaten.
3. I ate less food than Bill. - Grammatically correct. It suggests that the speaker consumed a smaller amount of food compared to Bill.
4. Bill ate more food than me. - Grammatically correct. This conveys that Bill consumed a larger quantity of food than the speaker.
5. I ate the least food in my class. - Grammatically correct. This means that the speaker ate the smallest amount of food compared to everyone else in their class.
6. I ate the least food of all my classmates. - Grammatically correct. It implies that the speaker consumed the smallest quantity of food when compared to all their classmates.
7. I ate the least food of all of us. - Grammatically correct. This suggests that the speaker consumed the smallest amount of food when compared to a specific group of people.

No errors were found in the given sentences. However, it's worth noting that sentences 1 and 2 have slightly different meanings. Sentence 1 implies a smaller quantity of food was eaten, possibly not enough, while sentence 2 simply indicates that some small amount of food was eaten.