例句與造句

1. Their working up period extended for about eight months before they were introduced into service, during which time modifications were continually made to them.
2. After a working up period ( during which her screws were damaged on 21 May 1943 ), her first patrol was to the Norwegian coast in June July 1943.
3. It's difficult to find working up period in a sentence. 用working up period造句挺難的