______ time went on , the weather got worse and worse

A mistake ______ have been made on our bill. We didn’t order any fish today.

Tom was so wild about computer games that he would stay online for ten hours _____every day.[ ]

d like to buy some good English reference books,but _______ was available from the bookstore, where I only found some Chineseones.

His mother sent _________ to a school when he was only 6.