$\"\"$

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The expression is $\"\"$ .

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The expression is in the form of $\"\"$ .

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Condier for different values of $\"\"$ .

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If $\"\"$ , $\"\"$ .

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If $\"\"$ , $\"\"$ .

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If $\"\"$ , $\"\"$ .

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If $\"\"$ , $\"\"$ .

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If $\"\"$ , $\"\"$ .

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Observe the values, for every $\"\"$ value haveing the same unit digit.

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Rewrite $\"\"$ .

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Hence, the unit digit of $\"\"$ is $\"\"$ .

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Therefore, the option $\"\"$ is the correct choice.

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$\"\"$

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The option $\"\"$ is the correct choice.