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The CIA flew new stealth drone planes on dozens of secret missions deep into Pakistan to monitor Osama bin Laden's compound before US commandos killed him, The Washington Post reported on Tuesday.

Citing current and former US officials, the Post said the Central Intelligence Agency (CIA) used the highly sophisticated unmanned planes to fly undetected at high altitudes and provide high-resolution video months before bin Laden was killed in a dramatic May 2 assault by US special forces.

"It's not like you can just park a Predator (drone) overhead - the Pakistanis would know," a former US official told the newspaper, noting the aircraft provided more enhanced surveillance than other available tools.

But the CIA was also using satellites, eavesdropping equipment and agency operatives based at a safe house in the garrison town of Abbottabad where bin Laden is believed to have lived for about five years until he was found, according to the Post.

The stealth drones provided imagery that US President Barack Obama watched with his national security team as the nighttime raid unfolded, the Post said. The aircraft can also eavesdrop on electronic transmissions so that US official could listen in on Pakistan's response.

Another stealth aircraft, a Black Hawk helicopter with specially designed cladding to dampen noise and avoid detection, was also used in the Abbottabad operation. But US forces destroyed it after a crash landing during the raid, leaving only a tail section behind.

US officials noted that Predators and other non-stealth surveillance aircraft could have been detected by Pakistani radar and other systems at military and nuclear facilities near bin Laden's compound.

The drones, which the Post suggested may have been Lockheed Martin's RQ-170 Sentinel model, can film at steep angles in all directions and so would not need to hover directly over their target.

Questions:

1. When was the assault by US special forces?

2. Where was bin Laden living?

3. What model of drones was used according to the Post?

Answers:

1. May 2.

2. Abbottabad.

3. Lockheed Martin's RQ-170 Sentinel model.

（中国日报网英语点津 Helen 编辑）

About the broadcaster:

Lee Hannon is Chief Editor at China Daily with 15-years experience in print and broadcast journalism. Born in England, Lee has traveled extensively around the world as a journalist including four years as a senior editor in Los Angeles. He now lives in Beijing and is happy to move to China and join the China Daily team.