Mark the correct alternative in each of the following:

The number of commutative binary operations that can be defined on a set of 2 elements is

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For the multiplication of matrices as a binary operation on the set of all matrices of the form , a, b ∈ R the inverse of is

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On the set Q⁺ of all positive rational numbers a binary operation * is defined by for all a, b ∈ Q⁺. The inverse of 8 is

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Let * be a binary operation defined on Q⁺ by the rule for all a, b ∈ Q⁺. The inverse of 4 * 6 is

Mark the correct alternative in each of the following:

The number of binary operation that can be defined on a set of 2 elements is