Which question would a social psychologist be least likely to research? in what situations do people tend to exhibit behavior? are people who are more trusting more likely to engage in behavior? how does temperature affect language perception? do individuals who are open to new experiences engage in more behavior?

1. I believe the answer is: In what situations do people tend to exhibit helping behavior?

Social psychologist study how the action of other people influence our behavior /emotions. If we observe closely ,The question above asked about how a situation (that has nothing to do with other people actions) could influence our action. 
This type of questions would most likely asked by humanistic psychologist, not a social psychologist

It’s either d or b ! but it might be b