Experts say the ability to take up lead is reduced when the pH level is above six and a half.

VOA: special.2009.06.09

It stood four to six meters tall, was about twelve meters long, and weighed up to seven tons.

VOA: special.2009.09.01

The "six" in the expression comes from the six feet that make up a fathom which is a little less than two meters.

VOA: special.2009.05.24

Ash up to three hundred meters thick covered more than six hundred square kilometers around the volcano.

VOA: special.2010.07.05

The "six" in the expression comes from the six feet that make up a fathom -- which is a little less than two meters.

VOA: special.2011.03.06

In one study,infected mothers began to take three anti-H.I.V.drugs while breastfeeding for up to six months.

VOA: special.2009.07.29

They were designed to fly at speeds up to six thousand four hundred kilometers an hour.

VOA: special.2010.07.07

"Rhonda Smith of Tennessee described how in two thousand six her Toyota-made Lexus sped up for a time to one hundred sixty kilometers an hour.

VOA: special.2010.02.26

The actions were conditions for additional government aid of up to six billion dollars.

VOA: special.2009.05.01

So America's space agency,NASA, said there was no reason to send up Gemini Six.

VOA: special.2009.07.01

Some of the mummies had signs of atherosclerosis in the inner walls of up to six arteries, the passages that lead blood away from the heart.

VOA: special.2009.12.15

The United States government has created possible flags that have up to fifty-six stars.

VOA: special.2010.04.02

He was born in Boston,Massachusetts in eighteen thirty-six and grew up in Cambridge.

VOA: special.2010.07.25

In fact,a hippo can stay under water for up to six minutes.

VOA: special.2009.08.19

Before then,the same trip might have taken up to six months.

VOA: special.2009.02.21

The Supreme Court took up the case in December, eighteen fifty-six.

VOA: special.2009.05.14

thirty-six feet per second up. Very smooth, very quiet ride."

VOA: special.2009.07.15

People stand and look up at the six men.

VOA: special.2010.05.31

"If children were exclusively breastfed for six months, continued to breastfeed up to two years, with appropriate additional food from six months onwards, we could save 1.5 million children under five years of age out the 8.8 million that we estimate to die currently every year."

VOA: special.2010.08.04