Photosynthesis is very useful. It feeds directly or indirectly every organism on planet,except few bacteria.
yes some chemical reactions are harmful to us. as digestion of food, photosynthesis, decomposition of organic waste are some examples of the useful chemical reactions.
lion are useful and harmful
It is not harmful. Also it is not useful
The changes talking place in our surroundings and which are useful to us are called Useful changes. The changes which are not useful but harmful are called Harmful changes
useful photosynthesis cooking food process of digestion harmful pollution rusting taking highly acidic food
useful
i think its both harmful and useful
Ozone at ground level is harmful. It is useful in stratosphere as it protects us from harmful UV rays.
It is useful because we can breathe it.
useful for dieing (;
It is USeful
changes both harmful and useful