Results when substances contaminate the air.

like this.

answering: it is all very simple. after you join you find many questions in the main page. you can click on answer if you know, then there will be a box written 'know the answer? add it here'. click on that and start writing your answer. don't copy answers from the net!

questioning: there will be an option for asking questions too. click on 'ask your question'. write your question there and give the correct subject and the number of points.

you will get points when you answer and also lose points when you question. you will get new ranks with many points and brainliest answers.