Sort the Following Events to Reflect the Order in Which

Short Answer

Sort the following events to reflect the order in which they occur during the formation of vesicles from the ER destined for the Golgi apparatus. Your answer would be a four-letter string composed of letters A to D only, e.g. DACB.
(A) Sar1 GTP hydrolysis
(B) Sar1 GTP binding
(C) Sar1-Sec23 binding
(D) Sar1 membrane association