If a Researcher Uses a Careful Matching Procedure in Correlational

Multiple Choice

If a researcher uses a careful matching procedure in correlational research, why can we still not draw conclusions about cause-and-effect relations between variables?

A) The measures may be unreliable.
B) A third variable influencing the relationship may have been missed.
C) The sample may not be a representative one.
D) Subject expectations may interfere with their behaviour
E) The Hawthorne effect is in effect.