Предлог или наречие.  
Once Mark Twain was sitting......a dinner party.........a well-known pianist. He said......him: It will interest you......a pianist that my life was once saved......a piano when I was a boy. We had a ter­rible flood ...... my home town. The water even reached the upper storey where I was ...... my father.......hesitation my father sat ...... a big chest ...... drawers, and floating ...... the river reached safely the bank." "Well, and you?" asked the pianist. "I accompanied him......the piano."
A Londoner who was going...... the West......England...... a holiday, arrived ...... train ......a town, and found that it waspouring.  He called a porter to carry his bags ...... a taxi.......the way...... the station, partly to make conversation and partly to get a local opinion ......prospects ......weather......his holiday, he asked the porter: "How long has it been raining like this?" "I don't know. Sir, I've only been here ......fifteen years," was the reply.