b$.$ How many different numbers can be placed in the$$ middle? Select the correct answer below and fill in the answer box to complete your choice.

$($Type a whole number. Use commas to separate answers as$$ needed.$)$

A$.$

One number can be placed in the middle. It is

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B$.$

Two numbers can be placed in the middle. They are

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enter your response here.

C$.$

Three numbers can be placed in the middle. They are

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enter your response here.

D$.$

Four numbers can be placed in the middle. They are

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enter your response here.