The water allows the plants to grow. Plants are just like humans they need food and water to live just like us.Also without food and water the plants will just dry out that is an example what can happen to us ,but we don't dry out we get sick because we don't drink or eat enough vitamins.
Energy is sunlight and it is use all around the world. It helps us all the time like this website it is powered by energy and without energy we won't have food. Sunlight is an example of energy plants need sunlight in order to grow also we need sunlight like plants.
What is oxygen ? Oxygen is what we mammals and so on breathe. Oxygen is made from plants. With out plants we will be dying and this is a reason why we should take care of plants . Also plants need use to because with out us we won't have air. Plants breathe in carbon dioxide to make oxygen.