What is wrong about the synthesis and assembly of collagen?

A、Theprocessofcollagensynthesisincellsis：mRNA→precursorchain+propeptide→pro-αchain→procollagen.;
B、PropeptideisauniquesequenceofC-terminalandN-terminalofprecollagenmolecules;
C、TheaminoacidsequenceofTypeⅠ,Ⅱ,ⅢcollagenpolypeptideisarrangedasGly-X-Ytripeptiderepeat.;
D、Collagenmoleculesaccumulatedirectlyintocollagenfibersthroughextracellularprocessing.