She says people might have difficulty completing an activity if they cannot expect some kind of reward in return.

VOA: special.2009.09.29

Today,the buildings are no longer there, just the outlines of where they stood, and some of the original bricks.

VOA: special.2010.04.26

Foreign students who will be attending graduate school can apply for some jobs before they come to the United States.

VOA: special.2009.01.29

They noted that some groups, as they move away from traditional ways of life, are developing diseases of modern living.

VOA: special.2009.07.20

Far below sea level, they contain some of the harshest environments on Earth, with no oxygen and no light.

VOA: special.2010.11.10

"Apple has been a driver in some things and they have been a faithful adopter of good ideas in others."

VOA: special.2011.01.28

Well,in some ways, they look like smaller versions of last month's wedding of Kate Middleton and Prince William in London.

VOA: special.2011.05.23

Passengers delayed on European airlines may be able to get back at least some of the money they had to spend.

VOA: special.2010.04.23

The students examine an issue, review what is already known, think about what they have learned and come to some conclusion.

VOA: special.2009.04.30

They decided that some parents were under too much social pressure to plan costly parties for their children.

VOA: special.2009.09.11

If this happens, people should remain in or near their car unless they see some kind of help.

VOA: special.2010.01.05

They are worried that some students will settle for vocational education when they could go to college and possibly earn more money.

VOA: special.2010.07.16

They can also see some of the things he used in his magic tricks, including a straitjacket and eleven pairs of handcuffs.

VOA: special.2010.12.17

The researchers did not try to identify the causes of the increase, but they have some theories.

VOA: special.2009.08.06