Final answer:
The expression of the 3x³-x²-x+4 is classified as a cubic equation because the highest power of the variable x is 3. Option B is the correct answer.
Step-by-step explanation:
The expression 3x³-x²-x+4 must be classified based on the highest power of the variable. In this case, since the highest power is 3, due to the term x³, this expression is classified as a cubic equation.
It is not quadratic, quartic, or linear because those classifications correspond to second, fourth, and first powers, respectively. To identify the type of algebraic expression, it is important to look for the highest exponent of the variable x. Therefore, the correct classification for the expression 3x³-x²-x+4 is (b) Cubic.