题干
When I _______ all the experiences that I have had around the world since _______ Doctors without Borders, I feel that I have been very lucky to be able to help others and do something ______.
| A．think back to; joining in; worthy |
| B．think over; joining; worthwhile |
| C．think back to; joining in; worthwhile |
| D．look back on; joining; worthwhile |
答案(点此获取答案解析）
