Which of the Following Is (Are) True Of $f ( x ) = 3 x ^ { 2 / 3 } - 2 x ?$

Multiple Choice

Which of the following is (are) true of $f ( x ) = 3 x ^ { 2 / 3 } - 2 x ?$
(I) f is decreasing on (1, ?)
(II) (1, f(1) ) is a relative minimum point
(III) f is concave down everywhere
(IV) (0, 0) is an inflection point

A) I and III
B) I, II, and III
C) II, III, and IV
D) I, III, and IV
E) all of these