CNN News:泰国反政府示威升级 局势令人堪忧

A new month, a new week and a new day.

Welcome to CNN STUDENT NEWS.

We're starting December in Thailand.

The country is a constitutional monarchy.

That means it has a king.

The government is run by an elected prime minister.

Right now, that prime minister is Yingluck Shinawatra.

Some people in Thailand want her out of power.

They say she's a puppet for her brother.

He was prime minister until he was forced out of power and convicted of corruption.

Yingluck Shinawatra denies the accusation against her.

Her critics have been calling for her to step down for weeks.

Yesterday, protesters tried to force their way into government headquarters in Bangkok.

On Friday, they jumped the gate at the army headquarters, demanding help to overthrow thegovernment.

For the most part, the protests have been peaceful, but on Saturday, four people were killedwhen protesters fought with Prime Minister Shinawatra's supporters.

Each side blames the other for starting the violence, but the situation in Bangkok is tense.

The tear gas canisters are starting once again, and you can see everyone starts to run.

Look over here. Some of these tear gas canisters are actually being thrown back.

The police lines by the protesters. Watch the car.

Some of the protesters are actually firing straight back, as soon as they see the tear gascoming. Over here.

We have to try and get away from the tear gas at this point.

Otherwise we just can't keep reporting.

But you can see the sheer level of the tear gas that's here at the moment.

This basically disperses the crowds in a matter of minutes, but then they just come straightback once the tear gas actually clears.

So it's a very difficult situation here on the streets of Bangkok as you can see.

In the Bronx, a borough of New York City, investigators are trying to figure out what caused apassenger train to jump off the tracks.

About 150 people were on board when it happened Sunday morning.

At least four were killed and more than 65 were injured.

By Sunday afternoon, authorities thought that all passengers were accounted for.

Seven of the eight cars were off the tracks.

At least two turned on their sides.

One car was just a few feet away from the Harlem River.

This happened in the same area where a freight train derailed in July.

Just the facts. HIV stands for Human Immunodeficiency Virus.

It interferes with the body's ability to fight off diseases, and it can cause AIDS, AcquiredImmunodeficiency Syndrome.

In 2012, more than 35 million people worldwide were living with HIV or AIDS.

There is no cure for HIV or AIDS, but medications can slow down the progress of the disease.