题目内容：

阅读理解。

On May 18，1969，NASA astronauts Thomas Stafford，John Young，and Eugene Cernan boarded the Apollo 10 lunar module(登月舱)—the fourth manned mission in the US Apollo Space program and only the second after Apollo 8 to circle the moon．Its mission was to circle the moon and thoroughly test the components and procedures to pave the way for the first lunar landing. The mission went perfectly without incident—at least that’s what every one believed.

However, that view has changed since February 22, after NASA released a digital recording of strange music heard by the space travelers．Then as they were re-entering the zone where they could communicate with ground control．One of the astronauts asked if they should report it．In response, Stafford expressed his doubts if anyone would even believe them．But they needn’t have worried. When NASA experts listened to the recordings，they thought the strange sounds were radio interference.

Michael Collins—the Apollo 11 pilot—said that the only reason why he was not shocked upon hearing them was that he had been forewarned by NASA officials．Collins also said that the music stopped as soon as the lunar module landed on the moon．

So why did it take NASA over 40 years to release the digital recording of the awful music only after it was featured in a recent television series NASA’s Unexplained Files? The US Space Agency says they have not been hiding them．In the press release that accompanies the release of the recording，NASA officials state，“The Apollo 10 audio clips were uploaded in 2012, but the mission’s sound recordings have been available at the National Archives for anyone that wanted to hear them since the early 1970s．”

Eugene Cernan, Apollo 10’s pilot who heard the sounds first，also released a statement saying，“I don’t remember that incident excited me enough to take it seriously．It was probably just radio interference．Had we thought it was something other than that，we would have briefed everyone after the flight. We never gave it another thought.”

While most people are ready to accept this logical explanation，there are some that believe otherwise. They guess the music proves the presence of aliens. Among them is Apollo 15 astronaut Al Worden，who thinks the sounds came from a source in outer space．In the episode of NASA’s Unexplained Files, which discusses the origin of the strange music，the astronaut says, “Logic tells me that if there was something recorded on there，then there was something there．”

1.Apollo 10’s mission was to ________.

A．take the astronauts to the moon

B．detect alien music in outer space

C．prepare for the landing on the moon

D．move around and observe the moon

2.When the astronauts heard the sounds, ________.

A．they were excited about the discovery

B．they reported to NASA

C．they were heading back to the lunar ground

D．they thought they might be of little importance

3.According to the passage, ________.

A．the mission of Apollo 10 turned out to be unsuccessful

B．NASA made the TV series to clarify some space-related mysteries

C．Al Worden on Apollo 15 believes in aliens and logic

D．Michael Collins knew about the strange sounds before his flight

4.What is the main idea of this passage?

A．A TV program was released about NASA’s unexplained files.

B．The music heard by Apollo astronauts could be radio interference.

C．NASA releases strange music heard by 1969 astronauts.

D．Apollo astronauts heard strange sounds from outer space.