試題詳解

19. Let A(r) be the area of a circle with a radius r. Assume that the worst-case time T(n) to execute a given program with input of size n is T(n) =n x A(n) = O(f(n)). What is the function of f(n)?
(A)n；
(B)n²,
(C)n³,
(D)n⁴.