Howdidyoutrytogettoschoolontime

問題詳情：

How did you try to get to school on time ______ you missed the school bus, Mary?

A. when                      B. if                            C. once                        D. that

【回答】

A

解析：用來引導時間狀語從句。

知識點：連詞

題型：選擇題