Which expression is a four-term polynomial of degree 6?

Correct answer: x⁶ − 2x⁴ + x − 3

To classify the expression, apply three rules: polynomial exponents must be non-negative integers, the degree is the greatest exponent with a non-zero coefficient, and terms are counted after combining like terms. Option A has four distinct terms: x⁶, −2x⁴, x, and −3. Its exponents are 6, 4, 1 and 0, all allowed, and its greatest exponent is 6. Therefore it is a four-term polynomial of degree 6. Option B is not a polynomial because it has the negative exponent −2. Option C has four terms but degree 5. Option D has the fractional exponent 6/5. Thus only option A satisfies both required conditions.