Plants naturally take in carbon dioxide they need for photosynthesis, the process of changing light energy to chemical energy.

VOA: special.2010.01.26

Yet sleep scientist Ying-Hui Fu at the University of California, San Francisco,says little is known about the basic need for sleep.

VOA: special.2009.08.26

The deputy executive director of UNICEF,Hilde Johnson, says the quake has only made the need for aid more immediate.

VOA: special.2010.02.15

And it can limit the need for chemical fertilizers by letting animal waste do the job of natural fertilizer.

VOA: special.2010.01.19

said people need to exercise thirty minutes each day for at least five days to get the health benefits of exercise.

VOA: special.2010.06.08

Studies have shown that over time, most humans need eight to eight and a half hours of sleep for the best health.

VOA: special.2009.08.26

Scientists at the agroforestry center say the use of fertilizer trees can reduce the need for chemical nitrogen by up to three-fourths.

VOA: special.2009.09.01

They say levels of a protein called Shh need to remain largely unchanged in a developing fetus for the palate to develop correctly.

VOA: special.2009.12.22

They teach the need for farming to improve the environment and make good use of natural resources.

VOA: special.2009.04.14

This form of grazing can reduce the need for pesticide treatments by reducing the growth of weeds.

VOA: special.2010.01.19

The hunger for news of the Civil War in the eighteen sixties increased the need for reporters.

VOA: special.2009.04.20

He stopped in many places to speak about the need for the League of Nations.

VOA: special.2010.11.18

"We'll need to wait for all the girls to enter puberty before we have a good grasp on what the contribution is of those environmental chemicals."

VOA: special.2010.08.18

He said the North Korean launch proves the need for nations to cooperate to stop the spread of nuclear weapons and to remove those that already exist.

VOA: special.2009.04.11