1. Famous poets and writers have claimed for centuries that love stems from powerful emotions. 2.
However, research has shown that feelings of love are at least in part influenced by various
chemicals in the brain. 3. One group of chemicals that is just beginning to be understood is the
pheromones-substances that promote sexual attraction in the opposite sex. 4. Experiments show
that males release a chemical in their sweat that has been shown to be highly appealing to women-
particularly during ovulation. 5. Similarly, women produce their own pheromones that draw men's
interest-one actually can raise the level of testosterone in a man's bloodstream. 6. In addition to
pheromones, another chemical, phenylethylamine (PEA), plays a crucial role in helping people fall"in
love." 7. Related closely to the addictive stimulant drugs called amphetamines, PEA actually causes
people to feel a high from their relationship. 8. The "heart-throbbing" sensations new lovers describe
and the feelings of excitement and infatuation that are part of new relationships are directly
attributed to this chemical. 9. As with many addictive drugs, eventually the body builds up a
tolerance to PEA and the strong feelings begin to wear off, usually within two years. 10. This
explains why infatuation cannot last forever. 11. A third group of chemicals-endorphins-appears to
be at work in long-term relationships. 12. Endorphins are the body's natural pain relievers. 13. In
addition, they produce a sense of security, tranquility, and calm. 14. During physical intimacy,
endorphins are released into the bloodstream, creating the feeling of satisfaction and security
common to long-term successful relationships.

The main idea of the above selection is:

A. Love is caused by various chemicals in the brain

Explanation:

in a place once known as north america, now known as panem, is a very rich city surrounded by twelve districts. every year because this very rich city, known as the capitol, is so rich and likes to think they control all the districts - which they do - there is something known as the hunger games! this is where two children, one boy and one girl from each district from the ages of twelve to eighteen, have to leave their families and compete in the hunger games, a live event that is aired on tv's all over panem. when katniss everdeen, aged sixteen from district 12, has to volunteer to take the place of her twelve-year-old sister prim after prim's name is called forth to become the 23rd member to compete in the 74th hunger games, she promises to prim that she will win! katniss doesn't believe she's coming out alive - but she's not going down without a fight.

because district 12 is so poor, katniss has been close to death many times from starvation but she's made it through it. but this is a different kind of close to death; this katniss doesn't know if she can survive.

she doesn't want to hurt, or kill anyone but when it comes down to it katniss' instinct is to survive. but when she starts to have confusing feelings about the boy from her district who is also her fellow contender, things get worse, and then she teams up with the girl from district 11 and only one person can survive. but who will it be? will her feelings get the better of her? will she let someone else win so they don't have to die? if katniss is going to win she's going to have to be brutal. she's going to have to kill!

because he is using a description to provide evidence to support his argument.

hope this could