You can ride your bike to school, but remember to be careful ____ .　　

This magazine isn't popular with the students though it____  every week.

It's difficult____  both the old and the young about the program at the same time.

The kids clapped and shouted ____ when the actor appeared.

Though he is very busy, he goes to the movies to relax____ 

The children are interested in playing the piano, so they need more____ 

The visitors ____  not to swim in this river for several times.

There are no students in the classroom. They ____  on the playground.

Thank you for____  the museum. We've learned a lot.

You must do more exercise, ____  twice a week.

当前，有不少专家认为：“华南虎在自然界已不存在可自我延续与恢复能力，人工繁育华南虎进行野化训练和放归自然，促进其种群复壮，是拯救华南虎的必然途径”．为此，我市于2008年在韶关市国家森林公园里建立了华南虎繁育研究中心，用以保护华南虎．请你判断该措施属于（　　）