Pleasant music is often played       classes to make students refreshed and relaxed for a while.

It is believed that if a book is ______, it will surely ______ the reader.

I can’t thank you too much for your kindness because without your help I        have won the first prize in the speech contest．

____ the risk of a shark attack, you should follow these suggestions.

.--- What can I do for?--- I’d like to buy a gift for my sister’s birthday, one at a proper price but of _____ great use and it’d better be ______ surprise.