問題詳情：
根據句意和漢語提示，在空白處填入一個適當的單詞。
51. Many Chinese people had to____________（取消）their trips in February because of COVID-19.
52. Have you read the report? Those____________（英雄） stories really touched me deeply.
53. The Chinese government has done a lot to control plastic____________（污染）in big cities.
54. It’ll take about two days to finish the project if everything goes____________（順利地）.
55. It is____________（不禮貌的） to push in before others while waiting for the bus.
【回答】
51. cancel 52. Heroes 53. pollution 54. smoothly 55. impolite
知識點：單詞拼寫
題型：完成句子
