Three people got killed by two explosions.—When was __________—________ was on April 15 __________ the 2013 BostonMarathon was being held．

178. This is the only article of those that______ written by him.

The faces of the four famous American presidents on Mount Rushmorecan be seen from a ______ of 60 miles.

We had much difficulty __________ home in the snowstorm

Have you ever seen Tom recently— ____. He often goes on business in Canada.