31 下列那些情況可幫助診斷真性多血症（polycythemia vera）？①Total red mass：male＞35 mL/kg andfemale＞32 mL/kg ②Total red mass：male＜25 mL/kg and female＜20 mL/kg ③Arterial oxygensaturation＜60% ④Splenomegaly ⑤JAK2 mutation
(A)①②③
(B)①③④⑤
(C)①②③④
(D)①④⑤