[单选题]
The following electron microgr hfyhezy , :rs;6le+:aa(hg)wikz:mw dow)) i/ ae.8qwph shows part of an exocrine pancreas cell. Which of the labelled structures is respon )h/qidw8 . iwk z)eamwwo()g:sible for the production of vesicles for exocytosis?