Write an equation for a function that has the graph with the shape of y=x², but upside-down and shifted left 3 units. Which of the following options correctly represents the equation of the function?

A) f(x) = -x² - 3
B) f(x) = -(x + 3)²
C) f(x) = -x² + 3
D) f(x) = (x - 3)²