Choose the words whose underlined part is pronounced differently from that of the others in each group

I. Choose the words whose underlined part is pronounced differently from that of the others in each group.

1. A. customer                   B. sticker                             C. student                           D. question
2. A. stay                             B. listen                               C. study                               D. start
3. A. stop                             B. castle                               C. station                             D. stamp
4. A. recycle                        B. reusable                         C. article                               D. usually
5. A. single                          B. plastic                              C. simple                              D. bottle
6. A. social                          B. people                             C. talk                                    D. useful