Answer
The answer is $\color{red}{f) 6x^2 + 7x^4 - 2x^3}$.
Work Step by Step
Remember that a leading coefficient is the coefficient of the polynomial with the highest degree.
In this item, the choice with 7 as its leading coefficient, when arranged is, $6x^2 + 7x^4 - 2x^3$ or $7x^4 - 2x^3+ 6x^2 $. The answer is $\color{red}{f) 6x^2 + 7x^4 - 2x^3}$.