If air pollution is not controlled, it can/will cause many problems.
Yes it's correct.
Yes, "controlled" is the correct spelling.
this is the sentence I prepared for a math competition, hours spent on complicated math problems every day.
"How are you" is a correct sentence.
the answer is a experiment that is controlled
Yes, this sentence is correct.
You are palpitating. This is a correct sentence.
nhio
To help prevent pollution people can walk, ride bikes and use public transportation.
The Aztec empire controlled the Yukon Territory in Mexico. (Note: although grammatically correct, the Yukon Territory is nowhere near Mexico.)
no it is not a correct sentence.
That sentence is grammatically correct.