28.一圓軸長L,圓軸單位長度之扭轉角為θ,扭矩為T,圓軸之剛性模數為G,圓軸直徑D,截面極慣性矩為J,則此軸之總扭角 為: (A)T/(GJ) (B)(GJ)/T (C)(TL)/(GJ) (D)(GJ)/(TL)