1. If you are busy , I'll leave you alone. условное предложение 1 типа. Если ты занят, я оставлю тебя одного.
2. If I lived in Moscow,I would visit you. условное предложение 2 типа. Если бы я жила в Москве, я бы навестила тебя.
3. If I lived near a wood, I would gather mushrooms. условное предложение 2 типа. (обратите внимание: перед словом mushrooms нельзя ставить неопределенный артикль - это мн. число!) Если бы я жила около леса, я бы собирала грибы.
4. If my friend had come to see me yesterday,I would have been wery glad. условное предложение 3 типа. (обратите внимание: в этом предложении у Вас много спеллинговых ошибок - правописание) - Если бы мой друг навестил меня вчера, я была бы счастлива.
The inviroment is very important for me. My life and the life of the next generation are depended on the inviroment. Our nature plays the great role in our life. That's why we must save oceans, rivers, seas, lakes, forests and animals. We mustn't pollute water. We mustn't kill animals. We mustn't cut down the trees. We must think about our future and the future of our planet. I think I am too small to change something. But when I walk in the park or in the forest I never drop litter. I don't make fire in the forest. I always turn off water and electricity. I think that if every person do the same as me the world will change. I think that if you want to change something you must begin with youself. I think that the inviroment is a big problem and we must think about it and od something.
There is streets an under the underground of London.