Answer:
a. Correlational research: correlation is different to causation; the relationships may be because of a third variable.
b. Overjustification effect: extrinsic motivators may reduce intrinsic motivators.
Step-by-step explanation:
a. A correlational research studies the relationship between 2 variables, without any external variables involved. In this case, the relationship might be thanks to a third variable.
b. Extrinsic refers to external motivators and in this case the extrinsic motivators might reduce the students' desire to read.