--What made your father throw up last night?-- I think the large quantities of wine _________.
This book is said to be a special one, as it ____ many events not found in other history books.
The students will discuss a number of cases ____ beginners of English fail to use the language properly.
— Sorry to have interrupted you. Please go on.— Where was I?— You ____ you didn’t like your present job.
We consider ____ absolutely necessary that we should open our door to the outside world.
She asked me __________I __________him the night before.