Free moving molecules
a. solids
b. liquids
c. elements
d. molecules

The free moving molecules are called liquids. Liquid is one of the state of matters that flows and even change its shape and form. This state of matter is hardly incompressible and has a relatively fixed volume. It is composed of small particles such as atoms, molecules and/or ions.  They have no regular and standard arrangement and causing them to move about, vibrate and slide past each other. Moreover, liquid is considered the intermediate phase between solid and gas in which particles are subject to intermolecular attraction having more space within them.

Sorry i think the answer is b

There is no reason to think the results are biased or not conducted properly but you should not assume the results are correct just because they were done in a laboratory so the answer would be c. it is likely to be reliable because the results support the conclusion presented.