(AP) - For weeks - months - the price of a barrel of oil marches skyward, and gas prices at the pump soar to frustrating heights.

And then, all of a sudden, oil prices plummet - down, say, $15 in just a few days.

So, naturally, prices at your corner gas station ... pretty much stay the same.

Does this make sense?

Curiosity about stubbornly high pump prices inspired one of three questions in this edition of "Ask AP," a weekly Q&A column where AP journalists respond to readers' questions about the news.

If you have your own news-related question that you'd like to see answered by an AP reporter or editor, send it to newsquestions@ap.org, with "Ask AP" in the subject line. And please include your full name and hometown so they can be published with your question.

I've heard that Barack Obama doesn't qualify as a natural-born U.S. citizen _ and can't serve as president _ because his one parent who was a citizen (his mother) hadn't lived in the U.S. for five years past her 16th birthday when Obama was born. Is this true?

Arnold Cate

North Carolina

This is one of the many myths about Obama that have been circulating on the Internet, and it's entirely untrue.

You do indeed need to be a natural-born citizen to serve as president _ and Obama, who was born in Hawaii, qualifies. The age and citizenship status of Obama's parents have nothing to do with his citizenship status; under the law, he's a natural-born citizen because he was born in the United States.

Some bloggers have raised similar questions about whether Sen. John McCain is eligible to run, since he was born in the Panama Canal Zone. He too is considered a natural-born citizen, since he was born on an U.S. military base in a place that was, at the time, a U.S. territory.

Just to put any concerns to rest, the Senate passed a resolution declaring that McCain is a natural-born citizen. The resolution _ submitted to the Senate by Obama and Sen. Hillary Rodham Clinton, among others _ passed by unanimous consent in April.

Donna Cassata

AP Political Editor

Washington

I understand, to some degree, the raising of gasoline prices when the price of a barrel of oil increases. What I can't understand is why we never see a significant drop in prices at the pump when the price of oil drops. Oh, there may be a penny less here or there, but nothing like the increases you see when oil prices go up. Why is that?

Joseph Patterson

St. Louis

The cost of oil does indeed affect what we pay at the pump, but the process of getting it from the well to your gas tank takes time. Prices take a while to catch up.

Oil future contracts being traded now _ the ones that hit new records last week but have since seen big drops _ are for oil that won't be delivered until next month. That oil still has to travel to a refinery, be broken down into gasoline and other products, and then get shipped again before it reaches your local filling station.

Another factor: Because of high oil prices, fuel refiners and retailers are making far less on a gallon of gasoline than they used to, and some are even losing money.

As much as gasoline prices have climbed, the refiners and retailers would like to have raised them even more to cover their costs _ but falling U.S. demand has made that impossible. And so, with an eye on their bottom line, they're not likely to lower their prices all that quickly _ even with oil prices declining sharply.

Adam Schreck

AP Energy Writer

New York

I was wondering: What backs our currency? I know it used to be the gold standard, but what about since that was done away with?

Elizabeth Frost

Oceanside, Calif.

No physical or concrete asset, such as gold or silver, backs modern-day U.S. currency.

Instead, it is backed by confidence that the Federal Reserve and the U.S. government will do their part to keep the economy, financial markets and inflation on an even keel.

People, consumers and businesses in the United States and beyond must have faith in the Fed's ability to keep prices stable. If prices remain stable and a low rate of inflation is maintained, people will feel confident that the dollar they use to buy goods and services today will buy a similar amount in the future. Similarly, people and investors need to believe that the U.S. economic, financial and political systems will remain stable because problems in those areas can erode confidence in the greenback.

U.S. citizens haven't been able to exchange their dollars for U.S. bullion since the 1930s, when the government went off the gold standard as far as domestic exchange was concerned. International convertibility of dollars into U.S. gold was stopped in 1971.

Jeannine Aversa

AP Economics Writer

Washington

Have questions of your own? Send them to newsquestions@ap.org.