Dr. ingram deliberately varied the imageability of items on a list and later measured participants' recall of the items. dr. ingram conducted a(n) study.
a) correlational
b) naturalistic
c) experimental
d) observational

Dr. Ingram conducted an C. experimental study.

Explanation:

An experimental study is that in which the variables are in direct control of the researcher. He/she is in control of changing or adjusting them in order to reach an outcome.

Dr. Ingram varied the imageability of items on a list to measure the participants' recalling abilities. He is conducting an experimental study.

Let's see why the other options are not valid in this case:

answer; i believe the correct answer is enlightenment;

well considering i can't see the graph, it's probably prices