My father walked _____ in the room, looking as if he was thinking over something.

It was Feb 8 2014 （Beijing） ___the opening ceremonies of the 2014 Winter Olympics ___ in Russia．

It’s good to learn English by _____ English programs.

Kitty spends a lot of time after-schoolactivities, but Linda spends little time ____it.

The police always takeadvantage of dogs’ ____ sense of smell to search for something.