If Researchers Measure How Some Canadian Children Behave After Playing

If researchers measure how some Canadian children behave after playing a violent video game for 2 hours and then replicate the experiment with Asian,European,and African children and then with teenagers,the researchers would be using which justification of nonrandom sampling?

A) Sometimes generality does not matter.
B) Sometimes generality is the cause of the effect.
C) Sometimes generality can be determined.
D) Sometimes generality can be assumed.