In the NFL, having 12 men on the field when the ball is snapped will cost you five yards - and earn someone a stern talking-to from the coach.

So why does The Associated Press name that many players to its All-Pro football team?

That's one of the four reader-submitted questions being answered in this installment of "Ask AP," a weekly Q&A column where AP journalists respond to questions about the news.

If you have your own question about the news that you'd like to see answered by an AP journalist, send it to newsquestions@ap.org, with "Ask AP" in the subject line. Visit the ASKap web site.

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Q: With ethnic violence erupting in Kenya, much has been written about how the ethnic groups take reprisal against one another. Other than targeting an opposing tribe's neighborhoods, how can each group identify members of the other groups?

Miriam E. Sang

San Juan, Puerto Rico

A: It's not easy for even Kenyans to tell. Swahili and English give Kenyans languages that cut across ethnic lines. Intermarriage is not uncommon, further blurring the lines.

But people who have been neighbors for decades tend to know each other's ethnic histories, and some of the violence pits neighbor against neighbor. Mobs at road blocks demand identification, as names can indicate ethnic group.

Luos, unlike other groups, do not circumcise men, and there have been reports of attackers demanding proof of circumcision and even forcibly circumcising victims.

Donna Bryson

Deputy Editor, AP Europe & Africa Desk

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Q: Every day on the news I hear something like: "Seven troops were killed today" or "Fourteen troops were injured in a roadside bombing." Why does the news media refer to individual soldiers as "troops"? I always thought a troop was a group of soldiers.

Darlene J. Murphy

Jessup, Md.

A: By definition, "troop" refers to a group, such as a unit of soldiers or scouts. "Troops" is the plural. But, in the always-evolving American vernacular, it has come to mean either the members of a large military contingent or, more generally, a fighting force, as in: "U.S. troops expanded an offensive" or "An additional 30,000 troops were deployed to Iraq."

The AP Stylebook entry on "troop" advises: "When the plural appears with a large number, it is understood to mean individuals: There were an estimated 150,000 troops in Iraq."

When describing smaller and specific numbers, AP favors "soldiers" or, if appropriate, Marines or another title.

Brian Murphy

Iraq Editor, AP International Desk

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Q: What is the status of the plan to open a national nuclear waste repository at Nevada's Yucca Mountain?

R.G. Frano

Jersey City, N.J.

A: The Yucca Mountain nuclear waste dump is way behind schedule and opinions differ as to whether it will ever get built.

The 77,000-ton underground repository, planned for the desert 90 miles northwest of Las Vegas, was supposed to open in 1998. Now supporters are hoping for 2020.

Meanwhile, tons of spent nuclear fuel rods are piling up at reactors around the country.

Some believe Yucca Mountain will get built one way or another because that radioactive waste has to go somewhere.

A major barrier is Senate Majority Leader Harry Reid, D-Nev. He fervently opposes the dump and has been slow-walking it to death by annually slashing its budget. Reid wants to leave the spent fuel at reactor sites where it already is.

The 2008 presidential election could help determine the fate of the waste dump.

Republican Sen. John McCain supports the dump, while Democratic Sens. Hillary Rodham Clinton and Barack Obama both oppose it.

Erica Werner

Associated Press Writer, Washington

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Q: Why do you list 12 players in your AP All-Pro football team when everyone knows only 11 men are allowed on the field at a time? In particular, why do you list three running backs when, for the vast majority of teams, only one running back is usually on the field at a time?

Jeff Vanderslice

Plantation, Fla.

A: We list 12 players on each side of the ball in order to accommodate voters who prefer to vote for a fullback on offense and those who prefer two RBs, and to accommodate those who prefer the 3-4 defense to the 4-3. We don't claim the All-Pro team would take the field.

Making the All-Pro team is an honor for players' achievements at their position and because of the variety of offenses and defenses, it is easier to honor these stars in this way.

Also, if "running backs" is used to mean RBs & FBs combined (as it was in this question), I disagree that most teams have only one on the field all the time. Note that both Super Bowl teams carry fullbacks and generally start them along with their RBs.

Barry Wilner

AP Football Writer