The TV shows a baby's pram   rolling off a train platform as the mother makes a mad rush to save her son, but she is too late and it falls onto the rails in front of an incoming train. This heart-stopping scene happened yesterday at Ashburton station in Melbourne, Australia. But the story has a happy ending: the six-month-old baby survived with just a cut on his forehead, although the pram was dragged about 35 metres by the braking train. The nurse Jon Wright said the boy just "needed a feed and a sleep" and didn't need to stay in hospital. "Luckily, he was strapped   into his pram at the time, which probably saved his life. I think the child is extremely lucky, " Wright told theHerald Sunnewspaper after the baby was taken to hospital with minor injuries. Fortunately the train was already slowing down to stop at the station so it stopped quickly when the driver put on the brakes as soon as he saw the pram fall in front of him. Rail firm Connex is to look into how the pram rolled off the platform. The accident came one day after Connex started a child safety awareness activity warning parents to keep babies strapped into their prams at all times while on platforms. The accident happened at the same time as the "balloon boy "story in the US, in which a six-year-old Colorado boy was reported to be trapped in a flyaway balloon. However, he was later found hiding in the family's garage. Many people believe that it had all been a publicity _ by the parents. No such doubts surround the baby on the train platform. Why could the train stop quickly?
Because it had just begun to move. Because it was moving slowly at that time. Because the mother took measures quickly. Because the driver saw the pram fall.
Question: The TV shows a baby's pram   rolling off a train platform as the mother makes a mad rush to save her son, but she is too late and it falls onto the rails in front of an incoming train. This heart-stopping scene happened yesterday at Ashburton station in Melbourne, Australia. But the story has a happy ending: the six-month-old baby survived with just a cut on his forehead, although the pram was dragged about 35 metres by the braking train. The nurse Jon Wright said the boy just "needed a feed and a sleep" and didn't need to stay in hospital. "Luckily, he was strapped   into his pram at the time, which probably saved his life. I think the child is extremely lucky, " Wright told theHerald Sunnewspaper after the baby was taken to hospital with minor injuries. Fortunately the train was already slowing down to stop at the station so it stopped quickly when the driver put on the brakes as soon as he saw the pram fall in front of him. Rail firm Connex is to look into how the pram rolled off the platform. The accident came one day after Connex started a child safety awareness activity warning parents to keep babies strapped into their prams at all times while on platforms. The accident happened at the same time as the "balloon boy "story in the US, in which a six-year-old Colorado boy was reported to be trapped in a flyaway balloon. However, he was later found hiding in the family's garage. Many people believe that it had all been a publicity _ by the parents. No such doubts surround the baby on the train platform. Why could the train stop quickly?
A. Because it had just begun to move.
B. Because it was moving slowly at that time.
C. Because the mother took measures quickly.
D. Because the driver saw the pram fall.
Answer: