Riddle #520

Question: Using 3 periods (.) and 1 question mark (?) make this a logical and grammatically correct sentence:

"That that is is that that is not is not is that it it is"

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Question: What can be broken but never forgotten?

Question: What tastes better than it smells?

Question: People see through me, but none pass through without killing me. I can be anywhere, and can be seen double or single. What am I?