What area of physics deals with the behavior of subatomic particles?

Particle Physics.

"Particle physics," also known as "high energy physics" is the branch of physics that deals with the nature and relationships of particles that constitute matter and radiation.

The term "particle" can refer to any small component. However, in this case, it refers to the smallest detectable particles, which are subatomic particles. The dynamics of these particles are also studied by quantum mechanics.

answer:

d. because dr. laguardia selected a widely used measure, his study generalizes to has strong external validity. external validity has limited external validity. other applications of this measure.

the widely used measure that he applied to his experiment was the benton facial recognition test. it employed on to football players and as result, only players who suffered brain concussions did not pas this test. and although it has an external validity, it is limited because it isn't general to apply to other population.