The moment was captured by a photographer and was a source of inspiration for those who saw it. Yang, who saved several classmates with his bare hands, quickly became a national hero.

In the past two weeks the 17-year-old Beichuan No 1 Middle School student has been busy with interviews, television programmes and visiting Bo, who is receiving treatment in Chongqing .

But once he lies down with other schoolmates in a tent in a camp on the outskirts of Mianyang , laughter quickly dissolves into sobs.

'Why did the army troops and heavy machinery arrive as late as near the end of the second day? If they had come a day earlier, would most of my classmates have been saved?' he asks.

'Why did those cement walls break into so many tiny pieces and turn into crumbs in my bare hands? Did my classmates die because of a substandard building?

'If there was more advanced medical equipment and treatment at the local hospital, could Liao Bo have avoided amputation? Could more of my friends have saved their legs and arms?'

Without answers to these questions, the young man says he will never be able to sleep in peace.

'Whenever I close my eyes I see the faces of my classmates - so many, so familiar, so painful. I also see my best friend Liao Bo, who must rely on crutches for the rest of his life,' Yang said.

'There is nothing I can do to bring them back from death or injury, but they need an answer, and I will stand up to get them an answer.'

When the earthquake struck, Yang was in a county hall practising a dance with another classmate.

They survived the two minutes of terror without a scratch and ran to school to join their classmates. But when they reached the campus, they were struck by horror.

'Our building had completely fallen into pieces ... especially the classrooms,' he said.

'The pre-fabricated cement blocks all fell and crushed everything underneath them - desks, chairs and students.

'We ran to the top of the ruins and found ourselves standing right above our classroom. Many classmates were crying for help under my feet ... they were calling my name, asking me to save them, to pull them out because they were in great pain, bleeding a lot and unable to breath or move.

'I told them to calm down and said I would reach each one of them. But they keep calling and calling, and I felt more and more desperate because I only had my hands and the cement blocks were heavy.

'Finally we found a loose block in the middle and with the help of local residents we lifted it up. I will never forget what I saw below.'

Yang said his classmates were badly injured and some were dead.

A small team of soldiers arrived within a few hours, but they were so few that most of the rescue efforts fell to students and residents.

'I did not see large numbers of troops and machines coming in until late the next day. To most of my classmates, they came too late. What kept them from coming?'

What Yang did not know was that relying on the outdated advice of the China Earthquake Administration, the central government mistakenly directed nearly all rescue crews to Wenchuan , only to discover a few days later that Beichuan had suffered much more.

He dared not tell his friend Bo that he had heard of medical equipment that might have saved his leg had he been sent to a better hospital in Chengdu.

'I don't know whether I should tell him if it is the case. But as a friend I want him to know the truth.'

Yang is intelligent and polite and as long the conversation stays away from the earthquake, he smiles and tosses a basketball around.

He said a positive, relaxed front that he and most of the students tried to put on was the only way for them to cope with the tragedy.

Although his parents were alive, many of his relatives, including a cousin in the same year, were gone.

There are more than 1,000 students on the temporary campus, but Yang is the only one left from his class. They have not started lessons yet and they pass time by playing basketball and reading.

'It is easier to play basketball than to read because whenever I take out the textbook, I remember the happy times I had with my classmates and my tears start to blur everything.

'I hope that one day I can study at Shanghai Jiaotong University because I love Shanghai. My elder sister is a migrant worker in the city and when she came back she had shown me lots of pictures - the Oriental Pearl Tower, the Jin Mao Tower.

'I will study economics and become an entrepreneur in the future so I can have my own company and manufacture lots of good products for society.

'But I will never, ever become a government official.'