A study has shown that dairy cattle can increase their milk production by up to three percent after having soothing music played to them for twelve hours per day over a nine-week period.
一項研究表明,在九週內每天播放十二小時的舒緩音樂後,乳牛的產奶量最多可增加百分之三。
That was a difficult period in American history.
那是美國歷史上的一個困難時期。
You can't replace the comma with a period in this sentence.
您不能將這句話中的逗號替換為句號。
Tom worked here for a short period.
湯姆在這裡工作過一段時間。
You forgot to put a period at the end of the sentence.
你忘記在句子末尾加上句號。
In every period of transition this riff-raff, which exists in every society, rises to the surface, and is not only without any aim but has not even a symptom of an idea, and merely does its utmost to give expression to uneasiness and impatience.