It was not until 1911, _______ the first vitamin was identified, _______ people realized the importance of it.
--$ 500 ,but that is my last offer. --OK, it is a __________.
--Why did she spend so much time searching shop after shop only for a blouse? --Oh, she was very __________ about her clothes.
This book is said to be a special one, which __________ many events not found in other history books.
You shouldn’t keep silent when __________.
They talked for about an hour of things and persons ______ they remembered in the school.