Lindsey and Justin must survey a random selection of two girls and two boys for each 7th grade class to get the most accurate results, so the correct choice is B.
This is so because, since precise information is required regarding a particular group of students (7th graders), it would be correct to target members of that group to obtain the first samples of information.
That is, by going to the most reliable source, a more reliable sample would be obtained.
Learn more about statistics in https://brainly.com/question/11161989