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Today we got a call that a homeless man living in the park looked severely ill. We rushed to the site but by the time we got there he 1) .... (DISAPPEAR). I was overcome by the familiar feeling of disappointment and guilt. "If I had got there sooner, I 2) .... (FIND) him. Am I doing all I can 3) .... (HELP) all these people in need?" Questions like these often haunt my thoughts. Although I 4) .... (DO) volunteer work with the homeless for ten years, I still have moments of self-doubt.