This is a trivial matter.

difficult
easy
small
important

The correct answer is C. small.

A trivial matter is a matter that is of little importance or significance. It is something that is not worth worrying about or taking seriously.

Option A, difficult, is incorrect because a trivial matter is not difficult. It is something that is easy to do or understand.

Option B, easy, is incorrect because a trivial matter is not easy. It is something that is not worth doing or taking seriously.

Option D, important, is incorrect because a trivial matter is not important. It is something that is not worth worrying about or taking seriously.