I was wondering what to do and＿＿＿＿＿＿Mr. Wang came in. 

＿to my regret, I am unable to accept your warm invitation. 

_____ to the delight of the schoolchildren, they will have a longer winter holiday which falls a week earlier than they have expected.

She is quite a different girl _____ she was five years ago.

Qingdao is ＿＿＿＿＿＿＿ beautiful city in summer.