Do you know what an envelope __________?[ ]
A. be
B. is
C. are
答案：B
商品的二因素之间的矛盾只有通过商品交换才能解决。( )
The commissioner of a professional sports league dictated that teams could not put players on the field who had a greater than 20 percent chance of suffering a career-ending spinal injury during competition. The commissioner justified this decision as a way to protect players from injury while protecting the league from lawsuits. Which of the following, if true, would most undermine the effectiveness of the commissioner’s new policy ？（）
A. Spinal injuries can result in paralysis, loss of fine motor skills, and even death.
B. The previous year, more than seven players in the league suffered career-ending spinal injuries.
C. The players’ union agrees that the risk of injury is an inevitable part of playing the game at a professional level.
D. There is no scientifically valid method for determining the likelihood of any player suffering a career-ending spinal injury at any given time.
E. Players barred from playing because of this new regulation will be entitled to compensation for lost wages at a level determined by the commissioner’s office.
