Classify the function as linear or quadratic and identify the quadratic, linear, and constant terms.

f(x) = 6x2 + x − 12

A. quadratic function; quadratic term: −12x2; linear term: −6x; constant term: −12

B. linear function; linear term: x; constant term: −12

C. linear function; linear term: 6x2; constant term: −12

D. quadratic function; quadratic term: 6x2; linear term: x; constant term: −12