1)As for me, I'd like to join the 5th event
2)I think, that plant a tree day would be the most efficient, because it will be the first step in solving environment problems
3)I suppose that car free day will be the most difficult to organise and take part in, because most of the people totally depend on their own transport and they can't spend a day without it
4) We could substitute cars for bicycles. They are environmentally friendly
5) 1, If everybody plants a tree our planet will have a new "lungs"
2, If everybody refuses using a car for the day, we will save a lot of petrol
3, If everybody stops using electrcty, we will save natural resources
4, If everybody buys nothig for he day, the world ecomony will save money to help all sick people
5, If everybody smiles at all stranqers, they will pick themselves up