GWD 21-30 偶最后一道疑点题，至今仍不清楚说什么。borne out 是证实的意思，也就是说plastic sleds 更危险被证实。但原题中根本没有出现plastic sleds 和 wooden sleds 的比较，我另一个疑点是不是题目有错（应该不会的），时间上不清楚，说In the past,most children 用wooden sleds ，In the past指的是过去？ last winter ？还是ten years ago？
请斑竹解答，请NN们现身，谢谢。
In the past, most children who went sledding in the winter snow in Verland used wooden sleds with runners and steering bars. Ten years ago, smooth plastic sleds became popular; they go faster than wooden sleds but are harder to steer and slow. The concern that plastic sleds are more dangerous is clearly borne out by the fact that the number of children injured while sledding was much higher last winter than it was ten years ago.
Which of the following, if true in Verland, most seriously undermines the force of the evidence cited?
A. A few children still use traditional wooden sleds.
B. Very few children wear any kind of protective gear, such as helmets, while sledding.
C. Plastic sleds can be used in a much wider variety of snow conditions than wooden sleds can.
D. Most sledding injuries occur when a sled collides with a tree, a rock, or another sled.
E. Because the traditional wooden sled can carry more than one rider, an accident involving a wooden sled can result in several children being injured. | 
