____ by taking part in practice can the young people be toughened and hardened into steel

“The children are playing in the park.”The main structure of the sentence is______.

You look a bit worried .—-It’s raining , but I ________my umbrella at home .

I want to buy a piano of high quality, _____ I can practise on every afternoon.

（2014年福州市高三适应性练习）33.— Your sneeze tells me you may have a flu.— No. It’s just __________ I can’t stand the smell of the paint here.