._________alone in the large house, the little boy had to learn to survive by himself

How do you deal with the disagreement between the company and the customers? — The key _____ the problem is to meet the demand _____by the customers. [ ]

Great changes___ have taken place _____ in the city, and a lot of factories________

Three weeks having gone by, the cause of the accident _____ unknown to the public.[ ]

The gentleman ______ you told me yesterday proved to be a thief.[ ]