Eye injuries from paintball games have increased among children, even as the protective equipment for the sport has improved, according to a study released yesterday in the journal pediatrics.        The Federal Consumer Product Safety Commission estimated the number of emergency room visits for eye injuries caused by paintballs at 545 in 2001 and more than 1,200 in 2003. More than 40 percent of those injuries were believed to involve children, the study said.        Paintballs are fired at a speed of up to 300 feet a second, the study said. Being so small, they can fit inside the bones meant to protect the eye. The study's author, Dr. David A. Listman of St. Barnabas Hospital in the Bronx, said paintball shopping centers had generally switched to full face masks ,which have become more effective at protecting the eyes than earlier  _ . But most injuries now occur in backyard play, which is more likely to involve teenagers or children."The injuries being seen are mostly in people who did not wear the proper, or for that matter any, safety equipment,"Dr. Listman said.        Those injuries can involve permanent damage to sight, he said.        Dr. Listman said he believed that paintball guns should be restricted to regulated places. In the absence of such action, parents should limit children's access to the guns and insist on proper protection. Paintball guns"should be treated with the same respect as any other firearm,"he said"These are the only guns that are made to shoot at your friends." Paintballs may cause injuries mainly because of_.
their content and size their speed their shape their content and shape
Question: Eye injuries from paintball games have increased among children, even as the protective equipment for the sport has improved, according to a study released yesterday in the journal pediatrics.        The Federal Consumer Product Safety Commission estimated the number of emergency room visits for eye injuries caused by paintballs at 545 in 2001 and more than 1,200 in 2003. More than 40 percent of those injuries were believed to involve children, the study said.        Paintballs are fired at a speed of up to 300 feet a second, the study said. Being so small, they can fit inside the bones meant to protect the eye. The study's author, Dr. David A. Listman of St. Barnabas Hospital in the Bronx, said paintball shopping centers had generally switched to full face masks ,which have become more effective at protecting the eyes than earlier  _ . But most injuries now occur in backyard play, which is more likely to involve teenagers or children."The injuries being seen are mostly in people who did not wear the proper, or for that matter any, safety equipment,"Dr. Listman said.        Those injuries can involve permanent damage to sight, he said.        Dr. Listman said he believed that paintball guns should be restricted to regulated places. In the absence of such action, parents should limit children's access to the guns and insist on proper protection. Paintball guns"should be treated with the same respect as any other firearm,"he said"These are the only guns that are made to shoot at your friends." Paintballs may cause injuries mainly because of_.
A. their content and size
B. their speed
C. their shape
D. their content and shape
Answer: