In Text I, the word  do in the fragments: “when they do occur" (line 38); “they do not risk being faced" (lines 43-44) and “workers must do their job" (line 47) respectively, fulfill the role of
 -   A emphasis, auxiliary verb and main verb
-   B auxiliary in the two first instances and modal in the third
-   C modal, main verb and auxiliary verb
-   D main verb, emphasis and modal
-   E auxiliary, modal and emphasis
