Mister Weindruch says researchers do not know why reducing calories increases the length of life.

VOA: special.2009.09.01

They do not know why all these things were found together in one place.

VOA: special.2010.08.03

Scientists do not know why women are more at risk than men.

VOA: special.2009.04.14

Researchers do not know why happiness increases as people get older.

VOA: special.2010.08.03

Scientists do not know why women are more at risk.

VOA: special.2010.06.15

I do not know why I should fear death.

VOA: special.2010.07.10

Everybody answered the questions well, intelligently, while he - why, dear me - he did not know anything, so to speak.

VOA: special.2009.01.03

Everybody answered the questions well, intelligently,while he C why,dear me C he did not know anything, so to speak.

VOA: special.2010.03.27

why,when we do not sleep, we do not function well. We just do not know much about sleep at all."

VOA: special.2009.08.26

Doctors do not yet know why this is true.

VOA: special.2010.06.15

But in a recent BBC poll, two-fifths of those questioned said they did not even know why British forces are in Afghanistan.

VOA: standard.2009.11.10