PLEASE HELPgrammarical problem

The word "do" here act as an intensifier of remembering something. Just like when you say I'm very hungry and I'm hungry, "very" is an adjective to tell you how intensely hungry you are.

Do remember all, is a figure of speech often use by many to show surprise.
If you say : "John remember all words in the dictionary" it show that you're lesser surprised than saying "he do remember all the words in the dictionary."

分別 : 語氣+surprise

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