A Study of Injuries to In-Line Skaters Used Data from the National

A study of injuries to in-line skaters used data from the National Electronic Injury Surveillance System, which collects data from a random sample of hospital emergency rooms (ERs) . The researchers interviewed 161 people who came to ERs with injuries from in-line skating. The interviews found that 53 people had been wearing wrist guards, and 6 of these people had wrist injuries. Of the 108 people who had not worn wrist guards, 45 had wrist injuries.
What is the sample size?

A) 161
B) 108
C) 53
D) 51