Elena is working on a team project for her computer science class. Although the entire team is responsible for the project, some people do not feel personally responsible for contributing to it. Because of this, some team members do not complete their assigned tasks.
This is most likely due to:

a) group polarization.
b) groupthink.
c) social facilitation.
d) social loafing.

d-- social loafing

Explanation:

Social Loafing refers to an  act of irresponsibility displayed by individuals not contributing or putting less effort towards the accomplishment of a group task because they feel other people are there who could handle the task. In reality, however, such individuals may contribute or accomplish a task if they were solely responsible for.

Here, Elena who is working on a team project for her computer science class together with  some people who  do not feel personally responsible for contributing to it causing  some team members  not to  complete their assigned tasks is due to Social Loafing on the part of the individuals who do not contribute to the accomplishment of the task.

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.

d. i assume the underlined word is "role." reformat if it isn't.

explanation:

role is closest to part because when replacing words, "playing a vital decision," "playing a vital activity," and "playing a vital dollar" don't make logical sense. the only meaningful choice is "playing a vital part."

this fits one of merriam-webster's definitions of role: "a function or part performed especially in a particular operation or process."