An Advantage of Using a Mechanical Device,such as an Actometer,is

An advantage of using a mechanical device,such as an actometer,is that:

A) it permits a researcher to be free to measure other things in his or her study.
B) it is unhampered by the biases associated with a human observer.
C) it can assess a wide range of overt and covert behaviors.
D) it is easier than questionnaires to use with children.