What would a chemist use to measure exactly 25.5 cm^3 of dilute hydrochloric acid? A) Burette, B) Beaker, C) Measuring cylinder, or D) Pipette?

The beaker would not be good because it is hard to measure
accurately to a millimeter.  Pipettes generally are used to dispense liquids by the drop
and not for actually measuring the volume of a liquid.

Both
measuring cylinders (also called graduated cylinders) and burettes can be used to
measure volume.  With a graduated cylinder you add the liquid to the cylinder and read
the volume on the gradation lines etched into the side of the cylinder. Depending on the
cylinder you could accurately measure your volume this
way.

If you want to accurately measure the volume of a
liquid you are putting into another container, then the burette would be the best
choice.  Burettes are used, for example, to do acid-base titrations, and can measure the
volume of liquid released with great precision.

The
advantage with the burette is that you put the liquid into the burette, measure its
initial volume, and then dispense the liquid to get an exact amount.  If you put exactly
25.5 ml in a graduated cylinder and then transfer it to another container some of the
liquid will remain in the cylinder due to surface tension so you will not have the exact
amount you started with.

Overall, the burette will give you
the most exact measurement of any volume you want.