【正确答案】 C

【答案解析】[解析] 画线词组的原形call off为动词词组，意为“停止；取消”。A项的原形put off意为“推迟”，例：They decided to put off the meeting until after Christmas.他们决定将会议推迟到圣诞节后举行。B项的原形end意为“结束”，例：The match ended in a draw.那场比赛以平局收场。C项的原形cancel意为“取消”，例：Why was the baseball game cancelled yesterday?昨天的棒球比赛为什么取消了?D项的原形participate in意为“参加”，例：Did you participate in the discussion?你参加讨论了吗?故选C。