III. Cloze Test: Choose the best answer to complete each sentence.
Passage 1
        IAVI, the International AIDS Vaccine Initiative has been ____21____ alongside Scripps Research to comeup with an HIV vaccine. The two organizations have ____22____ the results for a crucial Phase I clinical trial. Anew vaccine approach was tested by researchers, involving a design to ____23____ HIV infections bystimulating the production of rare immune cells, which are vital for creating the correct antibodies in order tofight HIV. There were 48 participants ____24____ in the study, which were then divided into two groups: onehigh-dose group and one low-dose group. Within the groups, they received either the vaccine or a placebo, intwo doses over the course of two separate months. Of those who received the vaccine, 97% developed the right____25____ cells to respond to HIV infection.
【題組】21.
(A) work
(B) works
(C) worked
(D) working