It's very dangerous to swim at the pool 解释下为什么用to?是固定的吗?

It's very dangerous to swim at the pool 解释下为什么用to?是固定的吗? It may be dangerous to swim in the pool alone.改为同义句 It's dangerous to swim here.look at the sigh.OH ,I ________n It's very dangerous to swim in a d____ river.中应该填什么? It's dangerous to swim _____ at sea.这里应该填什么介词或副词? It is very dangerous to swim in the river.What can stop them 1.It's much ______(safe) to swim in the swimming pool than i He may be dangerous to swim in the pool alone=（）he( ) danger it's,swim,dangerous,to,alone(.) 连词成句 it's,swim,dangerous,to,alone 连词成句 To swim in this river is very dangerous(用IT作形式主语改写句子） 1.It's too dangerous to swim in the sea. 2.I have two studie