产后出血最常见的原因是A．子宫颈裂伤 B．胎盘部分剥离 C．.胎盘残留 D．子宫收缩

     Mabel Welton, 62, was in her living room when a piece of dark gray metal hit the roof of her home. 
     1            . Because her house in Hessle, UK lies under a flight path. However, after examining the piece,
the Royal Air Force (RAF) said that the metal was space junk that fell to Earth.
     2            . "We heard this sound and went outside and saw this hole in the roof," she said. "The metal
had broken two tiles and made a mess." Welton said that her granddaughter's boyfriend Richard Sutcliffe
had to "put on some oven gloves to get it because it was so hot."
    The Weltons gave the metal to the police. 3            .
    Last Thursday, the RAF said they learned that the metal was space rubbish. 4            .
    A great number of pieces from more than 5,000 old satellites are now in space. Most pieces have fallen
to earth without doing damage to people or houses.