英语听力精选进阶版 7578（在线收听）

President Obama is preparing to give a highly charged televised address which will propose an American Jobs Act designed to stem unemployment. Some reports say the package will include tax cuts, infrastructure projects and re-hiring of laid-off teachers and police. Our North America editor Mark Mardell reports.

Some suggest all this could cost as much as $400bn, and it's very unlikely the president will get the agreement of the Republicans, who control the House of Representatives, to any increase in spending. He is of course setting a political trap for them, daring them to defy measures that he will portray as helping ordinary Americans. But there are grave dangers for the president as well; proposing what he cannot deliver may not look like an active leadership. Commentators, the markets, his opponents don't have high expectations of the speech, but his potential supporters are less cynical and are desperately hoping this will be a pivotal moment.

Nato forces in Afghanistan say a BBC reporter killed in July was shot dead by a US soldier. Ahmed Omed Khpulwak, who reported for the BBC's Pashto service, died during a suicide attack in Uruzgan province. Initial reports suggested he was killed by the Taliban, but a Nato investigation now confirms that he was shot dead by an American who mistook him for a suicide bomber.

The BBC's director of Global News, Peter Horrocks, paid tribute to Mr Khpulwak. He said it was essential that journalists had the best possible protection so that the world could hear their stories. The Isaf spokesman Brigadier General Carsten Jacobson said the American soldier thought Omed Khpulwak was a danger.

"He was holding a technical gadget in his hand which happened to be his telephone probably, so the soldier believed that he was a suicide bomber, a third suicide bomber who was about to detonate himself, and therefore took action."

Aid workers say hundreds of African migrants are fleeing from Libya each day because of the fear of racially motivated attacks. Mark Doyle reports.

The black Africans now leaving Libya told the UN migration office they feared for their lives. They said all black people in Libya were now being seen as associated with the black mercenaries that had been fighting on the side of Colonel Gaddafi. The UN stopped short of directly blaming the anti-Gaddafi Transitional National Council forces for systematically targeting the black Africans. It said some of the attacks could have been spontaneous fights among local communities. But the UN said the new wave of xenophobic violence was definitely associated with the arrival of the anti-Gaddafi groups.

The deputy head of Libya's National Transitional Council has said the battle against Colonel Gaddafi's forces isn't over. In his first speech since moving to Tripoli, Mahmoud Jibril called on Libyans to be united and not attack each other as they face big challenges ahead. Forces loyal to Colonel Gaddafi have continued to show defiance in the town of Bani Walid. They fired rockets at opposition forces from the town, which is one of the former leader's last remaining bastions.

World News from the BBC

The Turkish Prime Minister Recep Tayyip Erdogan has intensified his country's diplomatic row with Israel. In an interview with the Arab TV station al-Jazeera, Mr Erdogan said that Turkish warships would provide an escort to any Turkish aid vessels to Gaza. Turkey has expressed growing anger over Israel's refusal to offer a full apology for its raid on a flotilla heading for Gaza last year, during which nine Turkish activists were killed.

A new controversial study of a couple of two-million-year-old skeletons suggests that humans may have evolved in a different place and earlier than previously thought. Here's our science correspondent Pallab Ghosh.

One of the big questions in human evolution is when and where did the first humans emerge. The favourite theory is that it happened in East Africa around two million years ago. But a detailed study of remains found in a cave in Malapa, near Johannesburg, has now challenged that view. The two-million-year-old specimen seem to have greater brain development, hands and teeth that are more human-like, and their pelvises are more suited to walking than any other pre-human creature found to date. Indeed, the traits are so human-like that some argue that these creatures may themselves be the very first of our kind.

The United States Justice Department has issued a strongly critical report of the police force in the US territory of Puerto Rico, calling it "broken" in a number of critical ways. A three-year investigation found a pattern of unconstitutional behaviour, including excessive use of force and illegal searches and arrests.

One of London's most popular art galleries, the Tate Modern, has announced ambitious plans to open previously unused parts of its building in time for the Olympics next year. The first phase of the project will include opening the old 300-metre oil tanks at the former power station, which the gallery's director Nicholas Serota said would be some of the most exciting spaces in the world for new art.