A researcher studies the relationship between two variables and determines the likelihood that a change in one variable will result in a change in the other. What type of research is this person conducting?

This question is incomplete. Here are the missing options:

The answer is 2. correlational study.

Explanation:

A correlational study seeks to understand the relationship between two variables. For example, a piece of research called "Smoking cigarettes may result in premature death" is likely based in a correlational study.

It's important to realise correlation is not the same as causation. In other words, finding that two variables are related does NOT mean one is the direct cause of the other.

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."

answer; group behavior;