(2014·昆明质检)The five rings on the Olympic flag________the union of the five continents and the meeting of athletes from all over the world.

Natural learning environments inspire a burning ________ to learn, the key to a productive lifestyle.

The Sanlu Milk Powder event is a clear indication that food safety is a big problem; nobody can ___ all foods are secure to us, but we are sure that the situation is turning for the better．

Getting your students ________ in classroom activities is vitally important. 

I can’t avoid ________ her.