The most densely populated European nation is the Vatican, located within Rome. It has 800 citizens with them living on a 0.17 miles squared, meaning there are 4,709 citizens per mile squared. This number might seem odd since it's much greater, but as Vatican is smaller than 1 mile, it cannot be compared without it becoming so big.
The answer is B. phosphodioxide. It is not a pollutant of fossil fuels.
Climate change is going to happen, because even without humans Earth's climate changes over time. Global warming is where green house gasses are caught in our atmosphere and the earth gradually warms up. Global warming can be stopped, or a least slowed, but climate change will happen no matter what.
