\_\_\_\_ struck, a tuning fork produces an almost pure tone, retaining its pitch over a long period of time.
AWhen is it
BWhen it is正確答案
COne is
DIs one
答案與詳解
為什麼答案是 B
When 為從屬連接詞，it 指代主句主詞 a tuning fork，is 搭配後方 struck 構成被動語態，結構完整且語序正確。
載入中…
When 為從屬連接詞，it 指代主句主詞 a tuning fork，is 搭配後方 struck 構成被動語態，結構完整且語序正確。
