Нужно в правильном времени поставить и еще с if и when. 1)if pollution (to disturb) the balance in nature all living things (not to live) in harmony. 2)if the air and the water are polluted. many species of plants and animals (to disappear) 3)we (to put) up a tent when we (to go) to the camp. 4)we (to go) camping we never (to make) campfires. 5)if we (not to pay) attention to pollution , our earth (not to be safe) to live in