The 31st president was Herbert Hoover.
Air pollution is when unwanted chemicals and poisonous substances are added to air, making it harmful to most organisms such as humans, plants, animals, etc... and even the atmosphere.
By different human activities, we add a lot
of smoke and dust into the air.
The biggest cause of air pollution is the use of fossil fuels.
These are mainly coal, petrol/diesel, and natural gas.
For example, if you have been in the car before and are stuck in traffic,
you will see fumes coming out of many vehicles.
These fumes are poisonous gasses that make the air polluted.
An absence of menstruation in a postpubescent female is known as amenorrhea. It is a state in which a woman of reproductive age loses her menstrual cycle. Very often athlethes lose their periods, because of losing too much energy, so the body has not enough energy to release an egg and to get the period.
Answer:
Yes, because they didn't have the laws settled yet.
Explanation:
The correct answer is: "a handbook of government statistics
".
Government statistics are collected using objective measurament techniques and published by an official source.
The other three sources are not official, and probably, not objective as well. On the first hand, the information contained in a press realease from a company or in a claim in a political commercial, is subjected to the profit-maximization interests of a private company. On the other hand, a blog entry is very likely biased by the subjective opinion of its author.
