Della believes she earned an "a" in chemistry because the test was easy and she made a lot of lucky guesses. it is likely that della has a(n) _____ locus of control.
Della has an external locus of control. This is evident, in her previous comments, as it appears she feels she is in control of the situation and her destiny. The choices are made of her free will and not "fate" or other abstract cause.
