More highways have been built in China，________it much easier for people to travel from one place to another. 

The missing boys were last seen _____ near the river.

It was all your own fault, so you can’t avoid ____ for it. 

I still remember ______ to the south where we attempted _____ the river, which proved to be dangerous. 

 There was less food for birds and also for the Prairie dog, an______holes in the ground.